US LEC CORP.
                     CERTIFICATE OF DESIGNATION RELATING TO
                      SERIES A CONVERTIBLE PREFERRED STOCK


         US LEC Corp., a Delaware corporation (the "Corporation"), acting
pursuant to Section 151 of the General Corporation Law of the State of Delaware,
does hereby submit the following Certificate of Designation relating to its
Series A Convertible Preferred Stock.

         FIRST:   The name of the Corporation is US LEC Corp.

         SECOND:  By unanimous consent of the Board of Directors of the
                  Corporation dated March 10, 2000, the following resolutions
                  were duly adopted:

         WHEREAS, the Corporation's Restated Certificate of Incorporation, as
amended, authorizes the issuance of Preferred Stock consisting of Ten Million
(10,000,000) shares, par value $.01 per share, issuable from time to time in one
or more series; and

         WHEREAS, the Board of Directors of the Corporation is authorized,
subject to limitations prescribed by law and by the provisions of Article IV of
the Corporation's Restated Certificate of Incorporation, to establish and fix
the number of shares to be included in any series of Preferred Stock and the
designation, rights, preferences, powers, restrictions and limitations of the
shares of such series; and

         WHEREAS, it is the desire of the Board of Directors to establish and
fix the number of shares to be included in a new series of Preferred Stock and
the designation, rights, preferences and limitations of the shares of such new
series;

         NOW, THEREFORE, BE IT RESOLVED, there is hereby created a series of the
Preferred Stock of the Corporation designated as Series A Convertible Preferred
Stock, par value $.01 per share (the "Series A Preferred Stock"), consisting of
364,406 shares (164,406 of which shall be available solely for the payment of
preferential dividends pursuant to the following Section 1.1) and having the
following voting powers, preferences, relative, participating, optional,
conversion and other special rights, and qualifications, limitations and
restrictions:

         1. DIVIDENDS.

         1.1 PREFERENTIAL DIVIDENDS. Preferential dividends on each share of
Series A Preferred Stock shall be cumulative and accrue (whether or not there
are profits or surplus available therefor) at the rate of 6% per annum on the
Accrued Value thereof (computed on the basis of a 360-day year of twelve 30-day
months) from the date of issuance of such share (or in the case of Series A
Preferred Stock issued as dividends, from the Dividend Payment Date applicable
to such dividend) until the earliest of (i) the date on which the Liquidation
Value of such share of Series A Preferred Stock is paid to the holder thereof in
connection with the liquidation of the Corporation, (ii) the date on which the
Corporation redeems such share of Series A Preferred Stock, (iii) the date on
which such share of Series A Preferred Stock is converted into shares of Class A
Common Stock or (iv) the date on which such share of Series A Preferred Stock is
otherwise acquired by the Corporation. All dividends on each share of Series A
Preferred Stock shall accrue daily but be payable and compound quarterly in
arrears on each Dividend Payment Date, commencing on the first Dividend Payment
Date after the date of issuance of such share. During the period commencing on
the Initial Issue Date and continuing through the twelfth Dividend Payment Date
thereafter, all such dividends shall be paid by the Corporation through the
issuance of additional shares of Series A Preferred Stock valued at the Stated
Value and not in cash. Thereafter, all such dividends shall, at the option of
the Corporation, be paid on any Dividend Payment Date through either (x) the
issuance of additional shares of the Series A Preferred Stock valued at the
Stated Value, or (y) the payment of cash legally available for payment thereof,
whether or not such dividends have been declared; provided, however, that all
dividends payable on the Series A Preferred Stock, Option Preferred Stock and
Series C Preferred Stock on any given Dividend Payment Date must either all be
paid in cash or all be paid in additional shares of the applicable series of
preferred stock. If and when any shares of Series A Preferred Stock are issued
under this Section 1.1 for the payment of dividends, such shares of Series A
Preferred Stock shall be deemed to be validly issued and outstanding and fully
paid and nonassessable. Each such dividend shall be payable to the holders of
record of shares of the Series A Preferred Stock on the Dividend Payment Date,
as they appear on the stock records of the Corporation at the close of business
on such record dates.

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         1.2 PARTICIPATING DIVIDENDS. In addition to preferential dividends
payable under Section 1.1, holders of Series A Preferred Stock shall share pro
rata with holders of Common Stock, on the basis of the number of shares of
Common Stock which each holder of Series A Preferred Stock would be entitled to
receive upon conversion of the holder's Series A Preferred Stock into Common
Stock as of the record date for the dividend or distribution in accordance with
Section 4 (without giving effect to the one-year limitation on conversion), in
all other dividends and distributions, if any, that the Corporation's board of
directors may declare from time to time with respect to the Common Stock;
provided, however, that the holders of Series A Preferred Stock shall not be
entitled to participate in any stock dividend or distribution pursuant to this
Section 1.2 if, as a result of such stock dividend or distribution, the
Conversion Price is adjusted pursuant to Section 4.3.

         2. LIQUIDATION.

         Upon any liquidation, dissolution or winding up of the Corporation (a
"Liquidation"), each holder of Series A Preferred Stock shall be entitled to be
paid in preference to any distribution to holders of Junior Securities, but in
parity to any distribution to holders of Parity Securities, an amount in cash
(the "Liquidation Distribution") equal to the greater of (i) the product
obtained by multiplying the Liquidation Value of each share by the number of
shares of Series A Preferred Stock held by the holder or (ii) the amount that
would be payable to the holder in respect of the Common Stock issuable upon
conversion of the holder's shares of Series A Preferred Stock if all outstanding
shares of Series A Preferred Stock were converted into Common Stock immediately
prior to the Liquidation in accordance with Section 4 (without giving effect to
the one-year limitation on conversion). If, upon a Liquidation, the
Corporation's assets available for distribution to its stockholders are
insufficient to permit payment to holders of Series A Preferred Stock and Parity
Securities of the aggregate Liquidation Value of their Series A Preferred Stock
or the aggregate liquidation value of their Parity Securities, as applicable,
then the entire assets available for distribution shall be distributed among
holders of Series A Preferred Stock and Parity Securities pro rata on the basis
of the aggregate Liquidation Value of the Series A Preferred Stock or the
aggregate liquidation value of the Parity Securities, as applicable, held by
each holder before any payment is made to holders of Junior Securities. After
payment in full has been made to holders of Series A Preferred Stock and Parity
Securities of the aggregate Liquidation Distributions in respect of their Series
A Preferred Stock or the aggregate liquidation distribution in respect of the
Parity Securities, as applicable, any other series or class or classes of Junior
Securities shall be entitled to receive any and all assets remaining to be paid
or distributed to holders of capital stock of the Corporation, and holders of
Series A Preferred Stock and Parity Securities shall not share in any remaining
assets of the Corporation available for distribution. The Corporation shall mail
written notice of a Liquidation to each holder of record of Series A Preferred
Stock at least 30 days prior to the date for payment or distribution to
stockholders stated in the Corporation's notice. Solely for the purposes of this
Section 2, neither the sale, conveyance, exchange or transfer (for cash, shares
of stock, securities or other consideration) of all or substantially all of the
property or assets of the Corporation nor the consolidation or merger of the
Corporation with or into one or more other entities shall be deemed to be a
Liquidation.

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<PAGE>

         3. VOTING RIGHTS.

         3.1 ORDINARY VOTING. Except as otherwise required by law, the
Corporation's Restated Certificate of Incorporation or this Certificate of
Designation, holders of Series A Preferred Stock shall be entitled to vote with
holders of Common Stock, Option Preferred Stock and Series C Preferred Stock as
a single class on each matter submitted to a vote of the Corporation's
stockholders. Each share of Series A Preferred Stock shall have a number of
votes equal to the number of votes possessed by the number of shares of Class A
Common Stock into which the share of Series A Preferred Stock is convertible
(without giving effect to the one-year limitation on conversion) as of the
record date for determining the stockholders entitled to vote on the matter. Any
fractional voting rights that result (after aggregating, in the case of each
holder of Series A Preferred Stock, all shares of Class A Common Stock into
which all of the holders' shares of Series A Preferred Stock could be converted)
shall be rounded upwards or downwards to the nearest whole number (with one-half
being rounded upwards).

         3.2 ELECTION OF PREFERRED STOCK DIRECTORS. So long as Permitted Owners
hold at least 30% of the Underlying Common Stock, holders of Purchaser Preferred
Stock, voting separately as a single class to the exclusion of all other classes
of the Corporation's capital stock and with each share of Purchaser Preferred
Stock entitled to one vote, shall be entitled, in the election of directors of
the Corporation, to elect two directors to serve on the Corporation's board of
directors. Such directors shall comprise a third class of directors and be
referred to as "Preferred Stock Directors." Each Preferred Stock Director so
elected shall serve until his successor is duly elected by holders of Purchaser
Preferred Stock or he is removed from office by holders of Purchaser Preferred
Stock. If holders of Purchaser Preferred Stock for any reason fail to elect
anyone to fill any such directorship, the position shall remain vacant until
such time as holders of Purchaser Preferred Stock elect a Preferred Stock
Director to fill the position, and it shall not be filled by resolution or vote
of the Corporation's board of directors or its other stockholders. In the event
that Permitted Owners cease to hold at least 30% of the Underlying Common Stock
but continue to hold at least 20% of the Underlying Common Stock, the right and
power provided to holders of Purchaser Preferred Stock by this Section 3.2 shall
be limited to the election of only one Preferred Stock Director. In the event
that Permitted Owners cease to hold at least 20% of the Underlying Common Stock,
the right and power provided to holders of Purchaser Preferred Stock by this
Section 3.2 shall terminate.

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<PAGE>

         3.3 INITIAL TERM OF PREFERRED STOCK DIRECTORS. Each initial Preferred
Stock Director shall be appointed by the Board of Directors to serve until the
Corporation's annual meeting of stockholders in 2001 or until his resignation,
removal or death, or until his successor has been duly elected by holders of
Purchaser Preferred Stock. Thereafter, each Preferred Stock Director shall be
elected in accordance with Section 3.2 either (a) by written consent of the
holders of at least a majority of the outstanding shares of Purchaser Preferred
Stock or (b) at the annual meeting of stockholders.

         4. CONVERSION.

         4.1 CONVERSION PROCEDURE.

                  (a) At any time and from time to time beginning on the first
         anniversary of the Initial Issue Date, a holder of Series A Preferred
         Stock may convert all or any portion of the holder's shares of Series A
         Preferred Stock (including any fraction of a share) into a number of
         shares of Class A Common Stock computed by dividing (i) the aggregate
         Liquidation Value of the shares of Series A Preferred Stock to be
         converted by (ii) the Conversion Price then in effect; provided,
         however, that a holder of Series A Preferred Stock shall have the right
         to convert all or any portion of the holder's shares of Series A
         Preferred Stock as set forth above in the event of the occurrence of
         (i) an Acquisition Event or (ii) a Change of Control, in either case
         prior to the date of the first anniversary of the Initial Issue Date.

                  (b) Each conversion of Series A Preferred Stock shall be
         deemed to have been effected as of the close of business on the date on
         which the certificate or certificates representing the Series A
         Preferred Stock to be converted have been surrendered for conversion at
         the Corporation's principal office. When the conversion has been
         effected, the rights of the converting holder of Series A Preferred
         Stock as such holder shall cease, and the Person or Persons in whose
         name or names any certificate or certificates for shares of Class A
         Common Stock are to be issued upon the conversion shall be deemed to
         have become the holder or holders of record of the shares of Class A
         Common Stock represented thereby.

                  (c) As soon as possible but in any event within 10 Business
         Days after a conversion has been effected, the Corporation shall
         deliver to the converting holder: (i) a certificate or certificates
         representing the number of shares of Class A Common Stock issuable by
         reason of the conversion in such name or names and such denomination or
         denominations as the converting holder has specified; and (ii) a
         certificate representing any shares of Series A Preferred Stock which
         were represented by the certificate or certificates delivered to the
         Corporation in connection with the conversion but which were not
         converted.

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<PAGE>

                  (d) The issuance of a certificate or certificates for shares
         of Class A Common Stock upon the conversion of Series A Preferred Stock
         shall be made without charge to the converting holder for any issuance
         tax in respect of the conversion or other cost incurred by the
         Corporation in connection with the conversion and the related issuance
         of shares of Class A Common Stock. Upon conversion of each share of
         Series A Preferred Stock, the Corporation shall take all actions that
         may be necessary in order to ensure that the Class A Common Stock
         issued as a result of the conversion is validly issued, fully paid and
         nonassessable.

                  (e) The Corporation shall not close its books against the
         transfer of Series A Preferred Stock or of Class A Common Stock issued
         or issuable upon conversion of Series A Preferred Stock in any manner
         which interferes with the timely conversion of Series A Preferred
         Stock.

                  (f) If any fractional interest in a share of Class A Common
         Stock would, except for the provisions of this Section 4.1(f), be
         issuable upon any conversion of Series A Preferred Stock, the
         Corporation, in lieu of issuing the fractional share otherwise
         issuable, may pay an amount in cash to the holder of the fractional
         interest equal to the Market Price of the fractional interest as of the
         date of conversion.

                  (g) Notwithstanding any other provision of this Section 4, if
         a conversion of Series A Preferred Stock is to be made in connection
         with a Corporate Change, an Acquisition Event or a Change of Control or
         any other similar transaction affecting the Corporation and its capital
         stock, the conversion may be conditioned, at the election of the
         converting holder, upon the consummation of the Corporate Change,
         Acquisition Event or Change of Control or other such similar
         transaction affecting the Corporation and its capital stock, in which
         event the conversion shall not be deemed to be effective until the
         Corporate Change, Acquisition Event or Change of Control or other such
         similar transaction affecting the Corporation and its capital stock has
         been consummated.

         4.2 CONVERSION PRICE. The initial conversion price for Series A
Preferred Stock (the "Conversion Price") shall be $35. In order to prevent
dilution of the conversion rights granted under Section 4.1, the initial
Conversion Price for Series A Preferred Stock shall be subject to adjustment
from time to time pursuant to Sections 4.3, 4.4, 4.5 and 4.6.

         4.3 COMMON STOCK SUBDIVISION OR COMBINATION. If the Corporation at any
time subdivides (by a stock split, stock dividend, recapitalization or
otherwise) its outstanding shares of Common Stock into a greater number of
shares, the Conversion Price in effect immediately prior to the subdivision
shall be proportionately reduced; and if the Corporation at any time combines
(by reverse stock split or otherwise) its outstanding shares of Common Stock
into a smaller number of shares, the Conversion Price in effect immediately
prior to the combination shall be proportionately increased. Any adjustment of
the Conversion Price under this Section 4.3 shall become effective as and when
the subdivision or combination becomes effective.

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<PAGE>

         4.4 CORPORATE CHANGE. Prior to the consummation of any Corporate
Change, the Corporation shall make appropriate provisions (in form and substance
reasonably satisfactory to holders of a majority of the shares of Series A
Preferred Stock then outstanding) to ensure that each holder of Series A
Preferred Stock shall have the right to receive upon conversion of the holder's
Series A Preferred Stock, in lieu of the shares of Class A Common Stock that the
holder otherwise would have been entitled to receive upon conversion, the stock,
securities or assets that the holder would have received in connection with the
Corporate Change if the holder had converted the holder's Series A Preferred
Stock immediately prior to the Corporate Change. The Corporation shall also make
appropriate provisions (in form and substance reasonably satisfactory to holders
of a majority of the shares of Series A Preferred Stock then outstanding) to
ensure that the provisions of this Section 4 and Section 5 will continue to be
applicable to the Series A Preferred Stock (including, in the case of any
Corporate Change in which the successor or purchasing corporation is other than
the Corporation, an immediate adjustment of the Conversion Price to the value of
the Common Stock reflected by the terms of the Corporate Change, if the value so
reflected is less than the Conversion Price in effect immediately prior to the
Corporate Change). The Corporation shall not effect any Corporate Change unless,
prior to the consummation of the Corporate Change, the successor corporation (if
other than the Corporation) or the purchasing corporation assumes by written
instrument (in form and substance reasonably satisfactory to holders of a
majority of the shares of Series A Preferred Stock then outstanding) the
obligation to deliver to each holder of Series A Preferred Stock such shares of
stock, securities or assets that the holder is entitled to receive in accordance
with this Section 4.4.

         4.5 WEIGHTED AVERAGE ANTI-DILUTION PROTECTION. If, on or after the
Initial Issue Date, the Corporation issues or sells, or in accordance with
Section 4.6 is deemed to have issued or sold, any shares of Common Stock for a
consideration per share less than the Conversion Price in effect immediately
prior to the time of such issue or sale, then immediately upon such issuance or
sale the Conversion Price shall be reduced to the Conversion Price determined by
dividing (i) the sum of (x) the product derived by multiplying the Conversion
Price in effect immediately prior to such issue or sale by the number of shares
of Common Stock Deemed Outstanding immediately prior to such issue or sale plus
(y) the consideration, if any, received by the Corporation upon such issue or
sale, by (ii) the number of shares of Common Stock Deemed Outstanding
immediately after such issue or sale.

         Notwithstanding the foregoing and Section 4.6, there shall be no
adjustment in the Conversion Price as a result of:

                  (a) the issuance of shares of Common Stock upon the exercise
         of Options outstanding as of the date of filing this Certificate of
         Designation (including any repricing of such options so long as such
         options are not repriced to an exercise price per share that is less
         than the Market Price on the date of repricing); and

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<PAGE>

                  (b) by reason of any one or combination of the following:

                        (i)     the grant or repricing of Options which are
                                authorized to be granted or repriced under the
                                Corporation's existing stock option plan as of
                                the date of filing this Certificate of
                                Designation, as such plan may be amended,
                                replaced and supplemented, and which are granted
                                or repriced after the date of filing this
                                Certificate of Designation at an exercise price
                                not less than the Market Price on the date of
                                grant or repricing, and the issuance of Common
                                Stock pursuant to the exercise of such Options;

                        (ii)    the grant or repricing of Options which are
                                authorized to be granted or repriced under any
                                new stock option or other stock-based employee
                                incentive plan which is adopted by the
                                Corporation and approved by its stockholders
                                after the date of filing this Certificate of
                                Designation and which are granted or repriced at
                                an exercise price not less than the Market Price
                                on the date of grant or repricing, and the
                                issuance of Common Stock pursuant to the
                                exercise of such Options; and

                        (iii)   the issuance and sale of Common Stock at a price
                                per share that is less than the Market Price
                                pursuant to any employee stock purchase plan
                                adopted by the Corporation that satisfies the
                                requirements of Section 423 of the Code and is
                                approved by the Corporation's stockholders after
                                the date of filing this Certificate of
                                Designation;

                  provided, however, that the foregoing exceptions to the
         anti-dilution provisions of this Section 4.5 shall not apply to Options
         or shares granted, repriced or issued pursuant to clauses (b)(i), (ii)
         or (iii) or to Options repriced pursuant to clause (a) at a price less
         than the then applicable Conversion Price to the extent that all such
         Options and shares represent in the aggregate in any calendar year more
         than two percent (2%) of the number of shares of Common Stock of the
         Company outstanding (on a fully diluted basis) on the last day of
         December of the previous calendar year (as adjusted for events
         occurring pursuant to Section 4.3 after the last day of the previous
         calendar year);

                  (c) the issuance of shares of Class A Common Stock upon
         conversion or exercise of the Series A Preferred Stock, or the
         adjustment of the Conversion Price related to the Series A Preferred
         Stock;

                  (d) the issuance of shares of Series A Preferred Stock;

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<PAGE>

                  (e) the issuance of shares of Option Preferred Stock pursuant
         to the terms of the Option Agreement;

                  (f) the issuance of Class A Common Stock upon conversion of
         the shares of Option Preferred Stock issued pursuant to the terms of
         the Option Agreement, or the adjustment of the conversion price related
         thereto in accordance with the terms of the Option Stock Designation as
         in effect on the first date of issuance of Option Preferred Stock;

                  (g) the issuance of shares of Series C Preferred Stock;

                  (h) the issuance of Class A Common Stock upon conversion of
         the Series C Preferred Stock or the adjustment of the conversion price
         related thereto in accordance with the terms of the Series C
         Designation as in effect on the first date of issuance of Series C
         Preferred Stock;

                  (i) the issuance of Class A Common Stock as a result of the
         conversion of Class B Common Stock to Class A Common Stock; and

                  (j) any other events with respect to which holders of a
         majority of the outstanding shares of Series A Preferred Stock waive
         their rights under this Section 4.5.

         4.6 EFFECT ON CONVERSION PRICE OF CERTAIN EVENTS. For purposes of
determining the adjusted Conversion Price under Section 4.5, the following shall
be applicable:

                  (a) If the Corporation in any manner grants or sells any
         Options and the price per share for which Common Stock is issuable upon
         the exercise of such Options, or upon conversion or exchange of any
         Convertible Securities issuable upon exercise of such Options, is less
         than the Conversion Price in effect immediately prior to the time of
         the granting or sale of such Options, then the total maximum number of
         shares of Common Stock issuable upon the exercise of such Options or
         upon conversion or exchange of the total maximum amount of such
         Convertible Securities issuable upon the exercise of such Options shall
         be deemed to be outstanding and to have been issued and sold by the
         Corporation at the time of the granting or sale of such Options for
         such price per share. For purposes of this paragraph the "price per
         share for which Common Stock is issuable" shall be determined by
         dividing (A) the total amount, if any, received or receivable by the
         Corporation as consideration for the granting or sale of such Options,
         plus the minimum aggregate amount of additional consideration payable
         to the Corporation upon exercise of all such Options, plus in the case
         of such Options which relate to Convertible Securities, the minimum
         aggregate amount of additional consideration, if any, payable to the
         Corporation upon the issuance or sale of such Convertible Securities
         and the conversion or exchange thereof, by (B) the total maximum number
         of shares of Common Stock issuable upon the exercise of such Options or
         upon the conversion or exchange of all such Convertible Securities
         issuable upon the exercise of such Options. No further adjustment of
         the Conversion Price shall be made when Convertible Securities are
         actually issued upon the exercise of such Options or when Common Stock
         is actually issued upon the exercise of such Options or the conversion
         or exchange of such Convertible Securities.

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<PAGE>

                  (b) If the Corporation in any manner issues or sells any
         Convertible Securities and the price per share for which Common Stock
         is issuable upon conversion or exchange thereof is less than the
         Conversion Price in effect immediately prior to the time of such issue
         or sale, then the maximum number of shares of Common Stock issuable
         upon conversion or exchange of such Convertible Securities shall be
         deemed to be outstanding and to have been issued and sold by the
         Corporation at the time of the issuance or sale of such Convertible
         Securities for such price per share. For the purposes of this
         paragraph, the "price per share for which Common Stock is issuable"
         shall be determined by dividing (A) the total amount received or
         receivable by the Corporation as consideration for the issue or sale of
         such Convertible Securities, plus the minimum aggregate amount of
         additional consideration, if any, payable to the Corporation upon the
         conversion or exchange thereof, by (B) the total maximum number of
         shares of Common Stock issuable upon the conversion or exchange of all
         such Convertible Securities. No further adjustment of the Conversion
         Price shall be made when Common Stock is actually issued upon the
         conversion or exchange of such Convertible Securities, and if any such
         issue or sale of such Convertible Securities is made upon exercise of
         any Options for which adjustments of the Conversion Price had been or
         are to be made pursuant to other provisions of this Section 4.6(b), no
         further adjustment of the Conversion Price shall be made by reason of
         such issue or sale.

                  (c) If the purchase price provided for in any Options, the
         additional consideration, if any, payable upon the conversion or
         exchange of any Convertible Securities or the rate at which any
         Convertible Securities are convertible into or exchangeable for Common
         Stock changes at any time, a corresponding number of shares of Common
         Stock shall be deemed to have been issued and the Conversion Price in
         effect at the time of such change shall be immediately adjusted to the
         Conversion Price which would have been in effect at such time had such
         Options or Convertible Securities still outstanding provided for such
         changed purchase price, additional consideration or conversion rate, as
         the case may be, at the time initially granted, issued or sold. If such
         adjustment would result in an increase of the Conversion Price then in
         effect, however, such adjustment shall not be effective until 30 days
         after written notice thereof has been given by the Corporation to all
         holders of Series A Preferred Stock. For purposes of this Section
         4.6(c), if the terms of any Option or Convertible Security which was
         outstanding as of the date of filing of this Certificate of Designation
         are changed in the manner described in the immediately preceding
         sentence, then such Option or Convertible Security and the Common Stock
         deemed issuable upon exercise, conversion or exchange thereof shall be
         deemed to have been issued as of the date of such change; but no such
         change shall at any time cause the Conversion Price hereunder to be
         increased.

                  (d) Upon the termination or expiration of any Option or the
         termination of any right to convert or exchange any Convertible
         Security without the exercise of any such Option or right, the
         Conversion Price then in effect hereunder shall be adjusted immediately
         to the Conversion Price which would have been in effect at the time of
         such expiration or termination had such Option or Convertible Security,
         to the extent outstanding immediately prior to such expiration or
         termination, never been issued. If such expiration or termination would
         result in an increase in the Conversion Price then in effect, however,
         such increase shall not be effective until 30 days after written notice
         thereof has been given to all holders of Series A Preferred Stock. For
         purposes of this Section 4.6(d), the expiration or termination of any
         Option or Convertible Security which was outstanding as of the date of
         filing of this Certificate of Designation shall not cause the
         Conversion Price hereunder to be adjusted unless, and only to the
         extent that, a change in the terms of such Option or Convertible
         Security caused it to be deemed to have been issued after the Initial
         Issue Date.

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<PAGE>

                  (e) If any Common Stock, Option or Convertible Security is
         issued or sold or deemed to have been issued or sold for cash, the
         Consideration received therefor shall be deemed to be the amount
         received by the Corporation therefor (net of discounts, commissions and
         related expenses). If any Common Stock, Option or Convertible Security
         is issued or sold for a consideration other than cash, the amount of
         the consideration other than cash received by the Corporation shall be
         the fair value of such consideration, except where such consideration
         consists of securities, in which case the amount of consideration
         received by the Corporation shall be the Market Price thereof as of the
         date of receipt. If any Common Stock, Option or Convertible Security is
         issued to the owners of the non-surviving entity in connection with any
         merger in which the Corporation is the surviving corporation, the
         amount of consideration therefor shall be deemed to be the fair value
         of such portion of the net assets and business or then on-surviving
         entity as is attributable to such Common Stock, Option or Convertible
         Security, as the case may be. The fair value of any consideration other
         than cash and securities shall be determined jointly by the Corporation
         and the holders of a majority of the outstanding shares of Series A
         Preferred Stock. If such parties are unable to reach agreement within a
         reasonable period of time, the fair value of such consideration shall
         be determined by an independent appraiser experienced in valuing such
         type of consideration jointly selected by the Corporation and the
         holders of a majority of the outstanding shares of Series A Preferred
         Stock. The determination of such appraiser shall be final and binding
         upon the parties, and the fees and expenses of such appraiser shall be
         borne by the Corporation.

                  (f) The number of shares of Common Stock outstanding at any
         given time shall not include shares owned or held by or for the account
         of the Corporation or any Subsidiary, but the disposition of any shares
         of Common Stock so owned or held shall be considered an issue or sale
         of Common Stock.

                  (g) If the Corporation takes a record of the holders of Common
         Stock for the purpose of entitling them (i) to receive a dividend or
         other distribution payable in Common Stock, Options or in Convertible
         Securities or (ii) to subscribe for or purchase Common Stock, Options
         or Convertible Securities, then such record date shall be deemed to be
         the date of the issue or sale of the shares of Common Stock deemed to
         have been issued or sold upon the declaration of such dividend or upon
         the making of such other distribution or the date of the granting of
         such right of subscription or purchase, as the case may be.

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<PAGE>

                  (h) In case any Option is issued in connection with the issue
         or sale of other securities of the Corporation, together comprising one
         integrated transaction in which no specific consideration is allocated
         to such Option by the parties thereto, the Option shall be deemed to
         have been issued for a consideration of $.01.

                  (i) Upon the occurrence of an Event of Default described in
         Section 3.4 (b) or (c) of the Corporate Governance Agreement, the
         Conversion Price then in effect shall automatically be decreased by
         10%.

         4.7 NOTICES OF ADJUSTMENT. Within 10 Business Days of any adjustment of
the Conversion Price, the Corporation shall give written notice of the
adjustment to all holders of Series A Preferred Stock.

         5. REDEMPTIONS.

         5.1 MANDATORY REDEMPTION; REDEMPTION AT HOLDER'S OPTION.

                  (a) On April 11, 2010, the Corporation shall redeem all of the
         issued and outstanding shares of the Series A Preferred Stock at a
         redemption price equal to the aggregate Liquidation Value of the shares
         to be redeemed. The Corporation shall give written notice of the
         redemption to all holders of Series A Preferred Stock not more than 90
         nor less than 10 days prior to the date the redemption is to be made.
         Redemptions under this Section 5.1(a) shall be subject to the terms of
         the Corporation's outstanding indebtedness, and the Corporation shall
         have no obligation to redeem any shares of Series A Preferred Stock in
         violation of the terms of its outstanding funded indebtedness.

                  (b) At any time on or after the occurrence of a Change of
         Control and for a period of 60 days thereafter, each holder of Series A
         Preferred Stock shall have the right to require the Corporation to
         redeem all or a portion of the holder's Series A Preferred Stock at a
         redemption price equal to 101% of the aggregate Liquidation Value (the
         "Change of Control Amount") of the shares to be redeemed. Any holder of
         Series A Preferred Stock may exercise the holder's redemption right
         under this Section 5.1(b) by delivering to the Corporation at its
         principal office a written notice stating the holder's intention to
         exercise the holder's redemption right and the number of the holder's
         shares of Series A Preferred Stock to be redeemed. The Corporation
         shall be obligated to redeem the total number of shares of Series A
         Preferred Stock specified in the holder's redemption notice on the 30th
         Business Day following its receipt of the holder's notice (the "Change
         of Control Payment Date"). Redemptions under this Section 5.1(b) shall
         be subject to the terms of the Corporation's outstanding indebtedness,
         and the Corporation shall have no obligation to redeem any shares of
         Series A Preferred Stock in violation of the terms of its outstanding
         funded indebtedness.

                                       11
<PAGE>

                  (c) The Corporation covenants that, if any of its outstanding
         funded indebtedness prohibits a redemption pursuant to Section 5.1(a)
         or (b) and is prepayable, the Corporation will make commercially
         reasonable efforts to prepay any such indebtedness so that the
         foregoing redemptions can be made. The Corporation further covenants
         that it will make commercially reasonable efforts to include in the
         terms of any of its funded indebtedness a provision to the effect that,
         if the holders thereof do not require or waive a required prepayment or
         redemption upon a Change of Control, the redemption required by Section
         5.1(b) shall not be prohibited.

                  (d) If the Corporation is unable for any reason to make the
         full amount of redemption pursuant to Sections 5.1(a), including as a
         result of Section 5.3, the Corporation shall immediately take a Board
         Action and the Conversion Price in effect on the date on which such
         redemption was required to be made shall be reduced to the lower of (i)
         50% of the Conversion Price as of such date and (ii) the Market Price
         as of such date.

                  (e) If the holders of all of the issued and outstanding shares
         of the Series A Preferred Stock notify the Corporation of their intent
         to exercise their redemption rights pursuant to Section 5.1(b) and the
         Corporation is unable for any reason to redeem all of such shares,
         including as a result of Section 5.3, the Corporation shall immediately
         take a Board Action and the Conversion Price in effect on the date on
         which such redemption was required to be made shall be reduced to the
         lower of (i) 50% of the Conversion Price as of such date and (ii) the
         Market Price as of such date.

         5.2 REDEMPTION AT CORPORATION'S OPTION.

                  (a) At any time on or after April 11, 2003, the Corporation
         shall have the right to redeem all (but not less than all) of the
         outstanding shares of Series A Preferred Stock at a redemption price
         equal to the aggregate Liquidation Value of the shares to be redeemed,
         upon written notice of the proposed redemption to all holders of Series
         A Preferred Stock given at least 30 days prior to the proposed
         redemption date, if the Market Price of a share of Common Stock for 30
         consecutive trading days during the 90-day period immediately preceding
         the date of the Corporation's redemption notice is at least 150% of the
         Conversion Price then in effect (without giving effect to any change in
         Conversion Price pursuant to Section 4.6(i), 5.1(d) or 5.1(e));
         provided, however, that the Corporation may not exercise its redemption
         rights under this Section 5.2(a) unless the Market Price of a share of
         Common Stock on the redemption date also is at least 150% of the
         Conversion Price then in effect (without giving effect to any change in
         the Conversion Price pursuant to Section 4.6(i), 5.1(d) or 5.1(e)). The
         Corporation's exercise of its redemption rights under this Section
         5.2(a) shall be subject to the conversion rights under Section 4 of
         each holder of Series A Preferred Stock, who may exercise those rights
         at any time prior to the redemption date.

                                       12
<PAGE>

                  (b) Upon the occurrence of a Covenant Triggering Event, the
         Corporation shall have the right to redeem all (but no less than all)
         of the outstanding shares of Series A Preferred Stock at a redemption
         price equal to (i) 135% of the aggregate Liquidation Value of the
         shares to be redeemed if such redemption occurs on or prior to the
         first anniversary of the Initial Issue Date or (ii) an internal rate of
         return from the Initial Issue Date of 20% per annum compounded
         quarterly on the Stated Value of the Series A Preferred Stock (other
         than shares of Series A Preferred Stock issued as dividends in
         accordance with Section 1.1) (as determined in accordance with standard
         financial practice by the Corporation's independent auditors whose
         determination shall be, in the absence of demonstrable error, final) to
         each holder of Series A Preferred Stock if such redemption occurs after
         the first anniversary of the Initial Issue Date, upon written notice of
         the proposed redemption to all holders of Series A Preferred Stock
         given at least 30 days prior to the proposed redemption date; provided,
         however, that the Corporation may not exercise its redemption rights
         under this Section 5.2(b) unless it also redeems all (but not less than
         all) of the outstanding shares of Option Preferred Stock pursuant to
         the terms of Section 5.2(b) of the Option Stock Designation. The
         Corporation's exercise of its redemption rights under this Section
         5.2(b) shall be subject to the conversion rights under Section 4 of
         each holder of Series A Preferred Stock, who may exercise those rights
         at any time prior to the redemption date.

         5.3 PAYMENT OF REDEMPTION PRICE. For each share of Series A Preferred
Stock which is to be redeemed pursuant to Sections 5.1 or 5.2, the Corporation
shall be obligated on the redemption date to pay to the holder, upon the
holder's surrender at the Corporation's principal office of the certificate
representing the share to be redeemed, the full redemption price of the share in
immediately available funds. In the case of a redemption pursuant to Section
5.1(a), if the funds of the Corporation legally available for the redemption of
Series A Preferred Stock and Series C Preferred Stock on the redemption date are
insufficient to redeem the total number of shares of Series A Preferred Stock
and Series C Preferred Stock that the Corporation is required to redeem
(pursuant to Section 5.1(a) hereof and Section 5.1 of the Series C Designation),
those funds which are legally available shall be used to redeem the maximum
possible number of shares of Series A Preferred Stock and Series C Preferred
Stock pro rata among the holders of the shares to be redeemed on the basis of
the number of shares held by each holder. As and when following the redemption
date additional funds of the Corporation become legally available for the
redemption of Series A Preferred Stock and Series C Preferred Stock, the
Corporation shall immediately use such funds to redeem the balance of the shares
of Series A Preferred Stock and Series C Preferred Stock which the Corporation
became obligated to redeem on the redemption date but which it has not redeemed.
In the case of a redemption pursuant to Section 5.1(b), if the funds of the
Corporation legally available for the redemption of Purchaser Preferred Stock on
the redemption date are insufficient to redeem the total number of shares of
Purchaser Preferred Stock that the Corporation is required to redeem (pursuant
to Section 5.1(b) hereof and Section 5.1(b) of the Option Stock Designation),
those funds which are legally available shall be used to redeem the maximum
possible number of shares of Purchaser Preferred Stock pro rata among the
holders of the shares to be redeemed on the basis of the number of shares held
by each holder. As and when following the redemption date additional funds of
the Corporation become available for the redemption of the Purchaser Preferred
Stock, the Corporation shall immediately use such funds to redeem the balance of
the shares of Purchaser Preferred Stock which the Corporation became obligated
to redeem on the redemption date but which it has not redeemed. In the case of a
redemption pursuant to Section 5.2(a), the Corporation may not redeem any shares
of Series A Preferred Stock unless the funds of the Corporation legally
available for the redemption of Series A Preferred Stock are sufficient to
redeem the total number of the outstanding shares of Series A Preferred Stock.
In the case of a redemption pursuant to Section 5.2(b), the Corporation may not
redeem any shares of Series A Preferred Stock unless the funds of the
Corporation legally available for the redemption of Purchaser Preferred Stock
pursuant to Section 5.2(b) hereof and Section 5.2(b) of the Option Stock
Designation are sufficient to redeem the total number of outstanding shares of
Purchaser Preferred Stock.

                                       13
<PAGE>

         5.4 REISSUANCE OF CERTIFICATES. In the event that fewer than the total
number of shares of Series A Preferred Stock represented by any certificate are
redeemed upon a redemption pursuant to Section 5.1, the Corporation shall issue
a new certificate representing the number of unredeemed shares of Series A
Preferred Stock to the holder of those shares without cost to the holder
promptly after the holder's surrender of the certificate representing the
redeemed shares of Series A Preferred Stock.

         5.5 REDEEMED SHARES. Any shares of Series A Preferred Stock which are
redeemed by the Corporation shall be canceled and shall not be reissued, sold or
transferred.

         6. RESTRICTIONS AND LIMITATIONS.

         As long as any of the initial number of shares of Series A Preferred
Stock remain outstanding, the Corporation shall not, directly or indirectly,
including directly or indirectly through a subsidiary, take any of the following
actions without the affirmative vote or written consent of holders of a majority
of the shares of Series A Preferred Stock then outstanding:

                  (a) file any other certificate of designation or amend or
         restate this Certificate of Designation or the Corporation's Restated
         Certificate of Incorporation or by-laws (as each of them may be amended
         in compliance with this Section 6) in any manner that adversely affects
         the powers, preferences and rights of Series A Preferred Stock as
         designated in this Certificate of Designation (as it may be amended in
         compliance with this Section 6) (other than the filing of the Option
         Stock Designation and the Series C Designation);

                  (b) authorize or issue additional Senior Securities or Parity
         Securities (other than (x) Option Preferred Stock authorized and issued
         pursuant to the Option Stock Designation, (y) Series C Preferred Stock
         authorized and issued pursuant to the Series C Designation, and (z)
         issuances of Series A Preferred Stock in accordance with Section 1);

                  (c) issue (i) any convertible or redeemable stock or
         securities other than those that would, in the written opinion of
         counsel to the Corporation in form and substance reasonably
         satisfactory to the holders of a majority of the outstanding Series A
         Preferred Stock, be treated as common stock for federal income tax
         purposes, or (ii) any convertible debt securities;

                  (d) declare or pay any dividends on or declare or make any
         other direct or indirect distribution on account of any Junior
         Securities, or set apart any sum for any such purpose (other than
         pursuant to Common Stock subdivisions or combinations as described in
         Section 4.3);

                                       14
<PAGE>

                  (e) redeem, purchase or otherwise acquire for value any shares
         of its capital stock unless any such redemption, purchase or other
         acquisition would not, in the written opinion of counsel to the
         Corporation in form and substance reasonably satisfactory to the
         holders of a majority of the outstanding Series A Preferred Stock, be
         treated as the receipt of cash or property by stockholders for purposes
         of Section 305(b)(2) of the Code (other than (x) Series A Preferred
         Stock redeemed pursuant to Section 5, (y) shares of Option Preferred
         Stock issued pursuant to the Option Agreement and redeemed in
         accordance with Section 5 of the Option Stock Designation as in effect
         on the date of initial issuance of the Option Preferred Stock and (z)
         shares of Series C Preferred Stock redeemed in accordance with Section
         5 of the Series C Designation as in effect on the date of initial
         issuance of the Series C Preferred Stock); or

                  (f) redeem, purchase or otherwise acquire for value any shares
         of Series A Preferred Stock, except in accordance with Section 5.

         7. REGISTRATION AND TRANSFER.

                  (a) The Corporation shall keep at its principal office a
         register for the registration of Series A Preferred Stock. The
         Corporation may deem and treat the registered holder(s) of the Series A
         Preferred Stock as the absolute owner(s) thereof (notwithstanding any
         notation of ownership or other writing on the Series A Preferred Stock
         certificates made by any Person) for the purpose of any conversion
         thereof or any payment or distribution to the holder(s) thereof, and
         for all other purposes, and the Corporation shall not be affected by
         any notice to the contrary other than pursuant to Section 7(b). For the
         purpose of this Agreement, all references to a holder herein shall
         refer to a registered holder of Series A Preferred Stock.

                  (b) Upon the surrender of any certificate representing Series
         A Preferred Stock at the Corporation's principal office, the
         Corporation shall, at the request of the record holder of the
         certificate, execute and deliver (at the Corporation's expense) a new
         certificate or certificates in exchange representing in the aggregate
         the number of shares of Series A Preferred Stock represented by the
         surrendered certificate. Each new certificate shall be registered in
         the name and represent the number of shares of Series A Preferred Stock
         requested by the holder of the surrendered certificate and shall be
         substantially identical in form to the surrendered certificate. Any
         transfer of Series A Preferred Stock shall be subject, however, to any
         applicable contractual or other restrictions on transfer and the
         payment of any applicable transfer taxes by the transferring holder.

         8. REPLACEMENT.

         Upon receipt of evidence reasonably satisfactory to the Corporation
(e.g., an affidavit of the registered holder) of the ownership and the loss,
theft, destruction or mutilation of any certificate evidencing shares of Series
A Preferred Stock, and in the case of any such loss, theft or destruction, upon
receipt of indemnity reasonably satisfactory to the Corporation, or, in the case
of any such mutilation, upon surrender of the mutilated certificate, the
Corporation shall (at its expense) execute and deliver in replacement a new
certificate of like kind representing the number of shares of Series A Preferred
Stock represented by the lost, stolen, destroyed or mutilated certificate and
dated the date of the lost, stolen, destroyed or mutilated certificate.

                                       15
<PAGE>

         9. AMENDMENT AND WAIVER.

         No amendment, modification or waiver will be binding or effective with
respect to any provision of this Certificate of Designation without the prior
written consent of holders of not less than a majority of the shares of Series A
Preferred Stock outstanding at the time that the action is taken. No change in
the terms of this Certificate of Designation may be accomplished by merger or
consolidation of the Corporation with another corporation unless the Corporation
has obtained the prior affirmative vote or written consent of holders of not
less than a majority of the shares of Series A Preferred Stock then outstanding.

         10. NOTICES.

         The Corporation shall give written notice to all holders of Series A
Preferred Stock at least 20 days prior to the date on which the Corporation (a)
closes its books or takes a record (i) with respect to the payment of any
dividend or distribution to stockholders, (ii) with respect to any pro rata
subscription offer to holders of Common Stock or (iii) for determining rights to
vote with respect to any Liquidation or Corporate Change or (b) if no notice is
given pursuant to clause (a), consummates a transaction constituting a Corporate
Change. In addition, the Corporation shall give the notices required by Sections
2 and 4.7 and shall also give written notice to all holders of Series A
Preferred Stock at least ten Business Days prior to any Acquisition Event or
Change of Control. All notices, requests, claims, demands and other
communications ("Notices") under this Certificate of Designation shall be in
writing and sent by certified or registered mail, return receipt requested, a
recognized overnight courier service, telecopier or personal delivery, as
follows:

                  (a)      if to Corporation, to:

                                    US LEC Corp.
                                    Transamerica Square
                                    401 N. Tryon Street, Suite 1000
                                    Charlotte, North Carolina  28202
                                    Attention:       General Counsel
                                    Telecopier:      (704) 319-3098

                                       16
<PAGE>

                           with a required copy to:

                                    Moore & Van Allen, PLLC
                                    100 North Tryon Street, Floor 47
                                    Charlotte, North Carolina  28202-4003
                                    Attention:  Barney Stewart III
                                    Telecopier:  (704) 331-1151

                  (b)      if to any holder of Series A Preferred Stock (unless
                           the holder has otherwise indicated in writing), in
                           care of:

                                    Bain Capital, Inc.
                                    Two Copley Place
                                    Boston, Massachusetts 02116
                                    Attention:  Ian K. Loring
                                    Telecopier:  (617) 572-3274

                                                     and

                                    Thomas H. Lee Partners, L.P.
                                    75 State Street, 26th Floor
                                    Boston, Massachusetts 02109
                                    Attention:  Anthony J. DiNovi
                                    Telecopier:  (617) 227-3514

                           with a required copy to:

                                    Ropes & Gray
                                    One International Plaza
                                    Boston, Massachusetts  02110-2624
                                    Attention:  Philip J. Smith
                                    Telecopier:  (617) 951-7050

All Notices shall be deemed to have been duly given: when delivered by hand, if
personally delivered; when delivered by courier, if delivered by commercial
overnight courier service; five Business Days after being deposited in the mail,
postage prepaid, if mailed; and when receipt is acknowledged by the individual
to whom the telecopy is sent, if telecopied. A party may change its address for
purposes of this Agreement by Notice in accordance with this Section 10.2.

                                       17
<PAGE>

         11. DEFINITIONS.

         "ACCRUED VALUE" means, with respect to a share of Series A Preferred
Stock, the sum of (as adjusted for stock splits, stock combinations,
recapitalizations and similar events with respect to Series A Preferred Stock)
(i) $1,000, plus (ii) any dividends that have accrued on any Dividend Payment
Date and that have not been paid.

         "ACQUISITION EVENT" means (i) the Corporation has consolidated with, or
merged with or into, any other Person and, in connection with any such
consolidation or merger, the holders of the Common Stock outstanding immediately
prior to such transaction do not own, in the aggregate, at least 50% of the
outstanding stock of the surviving entity in such transaction, or (ii) any
Person has made a tender offer or exchange offer to acquire any of the Common
Stock (each such offer, a "Tender Offer"), and, upon the consummation of the
Tender Offer, the holders of the Common Stock outstanding immediately prior
thereto do not own, in the aggregate, at least 50% of the outstanding stock of
the Person that made the Tender Offer.

         "AFFILIATE" means, with respect to a Person, (a) any director,
executive officer, general partner, managing member or other manager of such
Person, (b) any other Person (other than a Subsidiary) which directly or
indirectly through one or more intermediaries, controls, or is controlled by, or
is under common control with, such Person and (c) if such Person is an
individual, any member of the immediate family (including parents, spouse and
children) of such individual, any trust whose principal beneficiary is such
individual or one or more members of such individual's immediate family and any
Person who is controlled by any such member or trust. The term "control" means
(i) the power to vote 25% or more of the securities or other equity interests of
a Person having ordinary voting power (on a fully diluted basis), or (ii) the
possession, directly or indirectly, of any other power to direct or cause the
direction of the management and policies of a Person, whether through ownership
of voting securities, by contract or otherwise.

         "BOARD ACTION" means (i) such action by the Corporation as is necessary
to cause the majority of the members of the Board (including any directors
elected pursuant to Section 3.2 hereof) to be persons designated by the
Permitted Owners of the Underlying Common Stock, including causing existing
members of the Board to resign and filling the vacancies created with such
designees or increasing the size of the Board and filling the vacancies created
with such designees or (ii) calling a special meeting of the Corporation's
stockholders for the purpose of electing such designees to fill such vacancies
if they are not filled as provided in clause (i). The action required by the
Corporation hereunder shall be taken as soon as practicable and shall include,
if required, adoption by the Board of any necessary amendments to the Bylaws,
the preparation and submission to the Corporation's stockholders of a proxy
statement in connection with any special stockholders' meeting and the filing of
any required reports with the United States Securities and Exchange Commission
and The Nasdaq Stock Market.

         "BUSINESS DAY" means any day other than a Saturday, Sunday or other day
on which commercial banks in New York City, New York or Charlotte, North
Carolina are authorized or required by law or executive order to close.

                                       18
<PAGE>

         "CHANGE OF BOARD" means an occurrence whereupon, at any time, fewer
than one-half of the directors comprising the board of directors of the
Corporation shall include members of a group consisting of any existing Board
members as the date of filing this Certificate of Designation with the Secretary
of State of Delaware, and replacement or additional directors nominated or
supported by one-half or more of the members of the foregoing group and any such
replacement or additional directors; provided, however, that, in the event the
Permitted Owners exercise their rights under Section 3.4 of the Corporate
Governance Agreement, such exercise shall not constitute a "Change of Board."

         "CHANGE OF CONTROL" means (i) the failure of Richard T. Aab ("Aab") and
Tansukh V. Ganatra ("Ganatra"), in the aggregate, to own or control, directly or
indirectly, stock of the Corporation representing at least 50% of the total
number of shares of voting capital stock of the Corporation (as adjusted for the
events described in Section 4.3) that they, in the aggregate, own or control,
directly or indirectly, as of the Initial Issue Date, (ii) the failure of Aab
and Ganatra, in the aggregate, to own or control, directly or indirectly, more
shares of the voting capital stock of the Corporation than any other Person or
group (other than a Permitted Owner or group of the Permitted Owners and their
Affiliates), within the meaning of Regulation 13D under the Securities Exchange
Act of 1934 or (iii) a Change of Board shall occur; provided, however, that if
either Aab or Ganatra dies and the survivor holds an irrevocable proxy to vote
the Class B Common Stock owned or controlled, directly or indirectly, by the
deceased stockholder as of the time of his death, then so long as such
irrevocable proxy remains in effect, such survivor shall be deemed to control
such Class B Common Stock for purposes of clauses (i) and (ii) so long as such
Class B Common Stock remains subject to such irrevocable proxy; and provided,
further, that upon the simultaneous death of Aab and Ganatra or upon the death
of the last to survive of Aab and Ganatra, if within 30 days of such deaths or
death all of the Class B Common Stock owned or controlled, directly or
indirectly, by Aab and Ganatra immediately prior to such deaths or death is
converted into Class A Common Stock by Permitted Transferees (as defined in the
Certificate of Incorporation) of Aab and Ganatra, such Class A Common Stock
shall be deemed to be controlled by Aab and Ganatra for purposes of clauses (i)
and (ii) so long as such Class A Common Stock is held by such Permitted
Transferees.

         "CHANGE OF CONTROL AMOUNT" has the meaning set forth in Section 5.1(b).

         "CHANGE OF CONTROL PAYMENT DATE" has the meaning set forth in Section
5.1(b).

         "CLASS A COMMON STOCK" means the Corporation's class A common stock,
par value $.01 per share, or any other capital stock of the Corporation into
which such stock is reclassified or reconstituted.

         "CLASS B COMMON STOCK" means the Corporation's class B common stock,
par value $.01 per share, or any other capital stock of the Corporation into
which such stock is reclassified or reconstituted.

         "CODE" means the Internal Revenue Code of 1986, as amended from time to
time, and the regulations promulgated and rulings issued thereunder.

                                       19
<PAGE>

         "COMMON STOCK" means Class A Common Stock, Class B Common Stock and any
other class of common stock created by the Corporation.

         "COMMON STOCK DEEMED OUTSTANDING" means, at any given time, (i) the
number of shares of Common Stock actually outstanding at such time, plus (ii)
the number of shares of Common Stock issuable upon conversion at such time of
the shares of Series A Preferred Stock, plus (iii) the number of shares of
Common Stock deemed to be outstanding pursuant to Sections 4.6(a) and 4.6(b),
whether or not the Options or Convertible Securities are actually exercisable or
convertible at such time.

         "COMPETITOR" means any Person that is (directly or through one or more
Affiliates) both (i) engaged in the business of providing telecommunication
services offered by the Corporation and its subsidiaries that generate at least
25% of the Corporation's consolidated revenues as of the date of the
Corporation's most recent Form 10-K or 10-Q filed with the United States
Securities and Exchange Commission and the revenues of such Person attributable
to such services exceed $50 million annualized and (ii) a competitor of the
Corporation operating in at least 25% of the MSAs (Metropolitan Statistical
Areas) in which the Corporation and its subsidiaries are operating as of the
time of the proposed Transfer.

         "CONVERSION PRICE" is defined in Section 4.2.

         "CONVERTIBLE SECURITIES" means any stock or securities directly or
indirectly convertible into or exchangeable for Common Stock.

         "CORPORATE CHANGE" means any capital reorganization, reclassification,
consolidation, merger or sale of all or substantially all of the Corporation's
assets to another Person which is effected in such a way that holders of Common
Stock are entitled to receive (either directly or upon a subsequent liquidation
of the Corporation) stock, securities or assets in respect of or in exchange for
Common Stock.

         "CORPORATE GOVERNANCE AGREEMENT" means that Corporate Governance
Agreement dated as of April 11, 2000 among the Corporation and the investors
listed on Schedule 1 attached thereto, as amended, supplemented or otherwise
modified.

         "COVENANT TRIGGERING EVENT" means the failure of the Permitted Owners
(as defined in the Corporate Governance Agreement) to consent to a transaction
contemplated by Section 3.1(i) or 3.1(j) of the Corporate Governance Agreement.

         "DIVIDEND PAYMENT DATE" means January 11, April 11, July 11 and October
11 of each year, beginning July 11, 2000.

         "INITIAL ISSUE DATE" means the first date on which any shares of Series
A Preferred Stock are issued hereunder.

                                       20
<PAGE>

         "INITIAL OPTION STOCK" means the aggregate number of shares of Option
Preferred Stock actually purchased and issued under the Option Agreement,
excluding any preferential dividends that accrue or are issued or paid pursuant
to the terms of the Option Preferred Stock.

         "INITIAL PREFERRED STOCK" means the 200,000 shares of Series A
Preferred Stock issued by the Corporation to the Purchasers pursuant to the
Purchase Agreement.

         "JUNIOR SECURITIES" means any class or series of capital stock or
series of preferred stock of the Corporation, the terms of which do not
expressly provide that it ranks senior to, or on a parity with, the Series A
Preferred Stock as to dividend rights and rights upon a liquidation, dissolution
or winding up of the Corporation.

         "LIQUIDATION" is defined in Section 2.

         "LIQUIDATION DISTRIBUTION" is defined in Section 2.

         "LIQUIDATION VALUE" means, with respect to a share of Series A
Preferred Stock, the sum of (as adjusted for stock splits, stock combinations,
recapitalizations and similar events with respect to Series A Preferred Stock)
(i) $1,000 plus (ii) all accrued and unpaid dividends on such share.

         "MARKET PRICE" of any security means the average (weighted by daily
trading volume) of the closing prices of such security's sales on all securities
exchanges on which such security may be listed at the time, or, if there has
been no sales on any such exchange on any day, or, if on any day such security
is not so listed, the average of the representative bid and asked prices quoted
in the NASDAQ System as of 4:00 P.M., New York time, or, if on any day such
security is not quoted in the NASDAQ System, the average of the highest bid and
lowest asked prices on such day in the domestic over-the-counter market as
reported by the National Quotation Bureau, Incorporated or any similar successor
organization, in each such case (except when the "Market Price" is being
determined for purposes of Section 5.2(a)) averaged over a period of 20 days
consisting of the day as of which the "Market Price" is being determined and the
19 consecutive Business Days prior to such day. If at any time such security is
not listed on any securities exchange or quoted in the NASDAQ System or the
over-the-counter market, the "Market Price" shall be the fair value thereof
determined jointly by the Corporation and the holders of a majority of the
shares of Series A Preferred Stock then outstanding. If such parties are unable
to reach agreement within a reasonable period of time, such fair value shall be
determined by an independent appraiser experienced in valuing securities jointly
selected by the Corporation and the holders of a majority of the shares of
Series A Preferred Stock. The determination of such appraiser shall be final and
binding upon the parties, and the Corporation shall pay the fees and expenses of
such appraiser. Notwithstanding the preceding: (i) an Option which is granted or
repriced at an exercise price equal to the last reported sales price of a share
of Common Stock on the Nasdaq National Market on the date of grant or repricing
shall be considered to have been granted or repriced at the Market Price on the
date of grant or repricing; and (ii) shares of Common Stock which are issued and
sold in an underwritten registered public offering shall be considered to have
been issued and sold at the Market Price.

                                       21
<PAGE>

         "OPTION AGREEMENT" means that Option Agreement dated as of April 11,
2000 among the Corporation and the purchasers listed on Schedule 1 attached
thereto, as amended, supplemented or otherwise modified.

         "OPTION PREFERRED STOCK" means the Series B Convertible Preferred Stock
of the Corporation, or any other capital stock of the Corporation into which
such stock is reclassified or reconstituted.

         "OPTION STOCK DESIGNATION" means the Certificate of Designation of the
Corporation relating to the Option Preferred Stock to be filed with the
Secretary of State of the State of Delaware in accordance with the terms and
conditions of the Option Agreement, as amended, supplemented or otherwise
modified.

         "OPTIONS" means any rights, warrants or options to subscribe for or
purchase Common Stock or Convertible Securities.

         "PARITY SECURITIES" means (i) the Option Preferred Stock, (ii) the
Series C Preferred Stock and (iii) any class or series of capital stock or
series of preferred stock of the Corporation, the terms of which provide that it
ranks on a parity with the Series A Preferred Stock as to dividend rights and
rights upon a liquidation, dissolution or winding up of the Corporation.

         "PERMITTED OWNER" means (i) a Purchaser, for as long as the Purchaser
continues to be the beneficial owner of any shares of the Underlying Common
Stock, and (ii) each Permitted Transferee, for as long as the Permitted
Transferee continues to be the beneficial owner of any shares of Underlying
Common Stock.

         "PERMITTED TRANSFEREE" means (i) any Affiliate of any Purchaser to whom
a Purchaser or another Affiliate of any Purchaser Transfers shares of Series A
Preferred Stock or Option Preferred Stock, (ii) any other Person to whom a
Purchaser or an Affiliate of any Purchaser Transfers shares of Series A
Preferred Stock or Option Preferred Stock with the prior written consent of the
Board of Directors, (iii) any Person to whom a transferee described in clause
(ii) Transfers shares of Series A Preferred Stock or Option Preferred Stock with
the prior written consent of the Board of Directors and (iv) any THL Holder and
any of the funds affiliated with Bain Capital, Inc. and any general or limited
partner of such funds; provided that in no event shall any shares of Series A
Preferred Stock or Option Preferred Stock be transferred to a Competitor or a
Person acting as a representative of a Competitor without the Corporation's
prior written consent.

         "PERSON" means an individual, partnership, corporation, limited
liability company, association, trust, unincorporated organization, or other
entity.

         "PREFERRED STOCK DIRECTOR" is defined in Section 3.2.

         "PURCHASE AGREEMENT" means the Preferred Stock Purchase Agreement dated
as of April 11, 2000 by and among the Corporation and the Purchasers listed on
Schedule 1 attached thereto, as amended, supplemented, or otherwise modified.

                                       22
<PAGE>

         "PURCHASER" or PURCHASERS" shall have the respective meanings given
such terms in the Purchase Agreement.

         "PURCHASER PREFERRED STOCK" means the Series A Preferred Stock and the
Option Preferred Stock.

         "SENIOR SECURITIES" means any class or series of capital stock or
series of preferred stock of the Corporation, the terms of which expressly
provide that it ranks senior to the Series A Preferred Stock as to dividend
rights and rights upon a liquidation, dissolution or winding up of the
Corporation.

         "SERIES C DESIGNATION" means the Certificate of Designation of the
Corporation relating to the Series C Preferred Stock to be filed with the
Secretary of State of the State of Delaware in such form as is permitted by the
Purchase Agreement, as amended, supplemented or otherwise modified.

         "SERIES C PREFERRED STOCK" means the Corporation's Series C Convertible
Preferred Stock, or any other capital stock of the Corporation into which such
stock is reclassified or reconstituted.

         "STATED VALUE" means, with respect to a share of Series A Preferred
Stock, $1000.

         "THL HOLDER" means (i) any general or limited partner of the THL
Entities (a "THL Partner") and any corporation, partnership, or other entity
which is an Affiliate of the THL Entities or any THL Partner (collectively, the
"THL Affiliates"), (ii) any managing director, general partner, director,
limited partner, officer or employee of the THL Entities or a THL Affiliate, or
the heirs, executors, administrators, testamentary trustees, lifetime trustees,
legatees or beneficiaries of any of the foregoing persons referred to in this
clause (iii) (collectively, "THL Associates"), (iv) a charitable institution as
defined in Section 501(c) of the Internal Revenue Code of 1986, as amended,
which receives a bona fide gift by a THL Associate of shares of Series A
Preferred Stock or Option Preferred Stock, (v) a bank, financial institution or
other lender which receives a bona fide pledge by a THL Associate of shares of
Series A Preferred Stock or Option Preferred Stock, and (vi) any trust, the
beneficiaries of which, or any corporation, limited liability company or
partnership, the stockholders, members or general or limited partners of which
include only the THL Entities, THL Affiliates, THL Associates, their spouses or
their lineal descendents. "THL Entities" shall mean Thomas H. Lee Partners, L.P.
and its affiliated entities.

         "TRANSFER" means to sell, assign, transfer (voluntarily or
involuntarily), exchange (by merger or otherwise) or otherwise dispose of or to
grant a lien, encumbrance, pledge or other form of security interest, except
that any Purchaser may create a security interest in shares of Series A
Preferred Stock or Option Preferred Stock to secure loans made to it so long as
any Transfer pursuant to such security interest is subject to the terms of the
Corporate Governance Agreement.

                                       23
<PAGE>

         "UNDERLYING COMMON STOCK" means all shares of Common Stock issued or
issuable upon conversion of (i) the Initial Preferred Stock and (ii) the Initial
Option Stock as of any date of determination (which number shall be determined,
with respect to any given date, based upon the Conversion Price or the
conversion price of the Option Preferred Stock, as applicable, in effect as of
such date without giving effect to the one year limitation on conversion)
without regard to any preferential dividends that accrue or are issued or paid
with respect to the Initial Preferred Stock pursuant to the Certificate of
Designation or the Initial Option Stock pursuant to the Option Stock
Designation.


                                       24
<PAGE>

         In witness, the Corporation has caused this Certificate of Designation
to be duly executed on April 7, 2000.

                                        US LEC CORP.,
                                        a Delaware corporation


                                        By /s/ Michael K. Robinson
                                           ----------------------------------
                                               Michael K. Robinson
                                               Executive Vice President, and
                                               Chief Financial Officer