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                                                                     EXHIBIT 4.3


                         [FORM OF SENIOR DEBT SECURITY]


                          [FACE OF [NOTE] [DEBENTURE]]

PRINCIPAL AMOUNT:  $___________
CUSIP: ___________
No.: __________

[Unless and until it is exchanged in whole or in part for [Notes] [Debentures]
in definitive registered form, this [Note] [Debenture] may not be transferred
except as a whole by the Depositary to the nominee of the Depositary or by a
nominee of the Depositary to the Depositary or another nominee of the Depositary
or by the Depositary or any such nominee to a successor Depositary or a nominee
of such successor Depositary.]

                     CREDIT SUISSE FIRST BOSTON (USA), INC.

                                   __% [Note]
                            [Sinking Fund Debenture]
                                 Due __________

            CREDIT SUISSE FIRST BOSTON (USA), INC., a Delaware corporation (the
"Company", which term includes any successor corporation under the Indenture
hereinafter referred to), for value received, hereby promises to pay to
________, or registered assigns, at the office or agency of the Company in New
York, New York, the principal sum of _______ dollars on _______________, in the
coin or currency of the United States, and to pay interest, semi-annually on
______ and ______ of each year, commencing __________, on said principal sum at
said office or agency, in like coin or currency, at the rate per annum specified
in the title of this [Note] [Debenture], from the _____ or the ______, as the
case may be, next preceding the date of this [Note] [Debenture] to which
interest has been paid or duly provided for, unless the date hereof is a date to
which interest has been paid or duly provided for, in which case from the date
of this [Note] [Debenture], or unless no interest has been paid or duly provided
for on these [Notes] [Debentures], in which case from __________, until payment
of said principal sum has been made or duly provided for; provided, that payment
of interest may be made at the option of the Company by check mailed to the
address of the person entitled thereto as such address shall appear on the
Security register or by wire transfer as provided in the Indenture.
Notwithstanding the foregoing, if the date hereof is after the __th day of _____
or ______ , as the case may be, and before the following _____ or ______, this
[Note] [Debenture] shall bear interest from such ______ or ______; provided,
that if the Company shall default in the payment of interest due on such _____
or _____, then this [Note] [Debenture] shall bear interest from the next
preceding _____ or _____, to which interest has been paid or duly provided for
or, if no interest has been paid or duly provided for on these [Notes]
[Debentures], from ________. The interest so payable on any ____ or ____ will,
subject to certain exceptions provided in the Indenture referred to on the
reverse hereof, be paid to the person in whose name this [Note] [Debenture] is
registered at the close of business on the ____ or ______, as the case may be,
next preceding such _____ or ______, whether or not such day is a Business Day.

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            Reference is made to the further provisions of this [Note]
[Debenture] set forth on the reverse hereof. Such further provisions shall for
all purposes have the same effect as though fully set forth at this place.

            This [Note] [Debenture] shall not be valid or become obligatory for
any purpose until the certificate of authentication hereon shall have been
manually signed by the Trustee under the Indenture referred to on the reverse
hereof.


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            IN WITNESS WHEREOF, CREDIT SUISSE FIRST BOSTON (USA), INC. has
caused this [Note][Debenture] to be duly executed under its corporate seal.


                                    CREDIT SUISSE FIRST BOSTON (USA), INC.


[SEAL]                              By:
                                       ---------------------------------
                                       Name:
                                       Title:




Attest:


By:
   -------------------------------
   Name:
   Title:



                          CERTIFICATE OF AUTHENTICATION

            This is one of the Securities of the series designated therein
referred to in the within-mentioned Indenture.

Dated:

                                          CHASE MANHATTAN BANK,
                                          as Trustee

                                          By:
                                             ---------------------------------
                                             Authorized Signatory


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                         [REVERSE OF [NOTE] [DEBENTURE]]

                     CREDIT SUISSE FIRST BOSTON (USA), INC.

                                   __% [Note]
                            [Sinking Fund Debenture]
                                    Due ____

            This [Note] [Sinking Fund Debenture] is one of a duly authorized
issue of debentures, notes, bonds or other evidences of indebtedness of the
Company (hereinafter called the "Securities") of the series hereinafter
specified, all issued or to be issued under and pursuant to a senior indenture
dated as of June 1, 2001 (herein called the "Indenture"), duly executed and
delivered by the Company to The Chase Manhattan Bank, as trustee (herein called
the "Trustee"), to which Indenture and all indentures supplemental thereto
reference is hereby made for a description of the rights, limitations of rights,
obligations, duties and immunities thereunder of the Trustee, the Company and
the Holders of the Securities. The Securities may be issued in one or more
series, which different series may be issued in various aggregate principal
amounts, may mature at different times, may bear interest (if any) at different
rates, may be subject to different redemption provisions (if any), may be
subject to different sinking, purchase or analogous funds (if any) and may
otherwise vary as in the Indenture provided. This [Note] [Debenture] is one of a
series designated as the ___% [Notes] [Sinking Fund Debentures] Due ___ of the
Company, limited in aggregate principal amount to $________.

            Interest will be computed on the basis of a 360-day year of twelve
30-day months. The Company shall pay interest on overdue Principal and, to the
extent lawful, on overdue installments of interest at the rate per annum borne
by this [Note] [Debenture]. If a payment date is not a Business Day as defined
in the Indenture at a place of payment, payment may be made at that place on the
next succeeding day that is a Business Day, and no interest shall accrue for the
intervening period.

            In case an Event of Default (as defined in the Indenture) with
respect to the ___% [Notes] [Sinking Fund Debentures] Due ____ shall have
occurred and be continuing, the Principal hereof and the interest accrued
hereon, if any, may be declared, and upon such declaration shall become, due and
payable, in the manner, with the effect and subject to the conditions provided
in the Indenture.

            The Indenture contains provisions which provide that, without prior
notice to any Holders, the Company and the Trustee may amend the Indenture and
the Securities of any series with the written consent of the Holders of a
majority in principal amount of the outstanding Securities of all series
affected by such amendment (all such series voting as one class), and the
Holders of a majority in principal amount of the outstanding Securities of all
series affected thereby (all such series voting as one class) by written notice
to the Trustee may waive future compliance by the Company with any provision of
the Indenture or the Securities of such series; provided that, without the
consent of each Holder of the Securities of each series affected thereby, an
amendment or waiver, including a waiver of past defaults, may not: (i) extend
the stated maturity of the Principal of, or any sinking fund obligation or any
installment of interest on, such Holder's Security, or reduce the principal
amount thereof or the rate of interest thereon

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(including any amount in respect of original issue discount), or any premium
payable with respect thereto, or adversely affect the rights of such Holder
under any mandatory redemption or repurchase provision or any right of
redemption or repurchase at the option of such Holder, or reduce the amount of
the Principal of an Original Issue Discount Security that would be due and
payable upon an acceleration of the maturity thereof or the amount thereof
provable in bankruptcy, or change any place of payment where, or the currency in
which, any Security of such series or any premium or the interest thereon is
payable, or impair the right to institute suit for the enforcement of any such
payment on or after the due date therefor; (ii) reduce the percentage in
principal amount of outstanding Securities of the relevant series the consent of
whose Holders is required for any such supplemental indenture, for any waiver of
compliance with certain provisions of the Indenture or certain Defaults and
their consequences provided for in the Indenture; (iii) waive a Default in the
payment of Principal of or interest on any Security of such Holder; or (iv)
modify any of the provisions of the Indenture governing supplemental indentures
with the consent of Securityholders except to increase any such percentage or to
provide that certain other provisions of the Indenture cannot be modified or
waived without the consent of the Holder of each outstanding Security affected
thereby.

            It is also provided in the Indenture that, subject to certain
conditions, the Holders of at least a majority in principal amount (or, if any
Securities are Original Issue Discount Securities, such portion of the Principal
as is then accelerable) of the outstanding Securities of all series affected
(voting as a single class), by notice to the Trustee, may waive an existing
Default or Event of Default with respect to the Securities of such series and
its consequences, except a Default in the payment of Principal of or interest on
any Security or in respect of a covenant or provision of the Indenture which
cannot be modified or amended without the consent of the Holder of each
outstanding Security affected. Upon any such waiver, such Default shall cease to
exist, and any Event of Default with respect to the Securities of such series
arising therefrom shall be deemed to have been cured, for every purpose of the
Indenture; but no such waiver shall extend to any subsequent or other Default or
Event of Default or impair any right consequent thereto.

            The Indenture provides that a series of Securities may include one
or more tranches (each a "tranche") of Securities, including Securities issued
in a Periodic Offering. The Securities of different tranches may have one or
more different terms, including authentication dates and public offering prices,
but all the Securities within each such tranche shall have identical terms,
including authentication date and public offering price. Notwithstanding any
other provision of the Indenture, subject to certain exceptions, with respect to
sections of the Indenture concerning the execution, authentication and terms of
the Securities, redemption of the Securities, Events of Default of the
Securities, defeasance of the Securities and amendment of the Indenture, if any
series of Securities includes more than one tranche, all provisions of such
sections applicable to any series of Securities shall be deemed equally
applicable to each tranche of any series of Securities in the same manner as
though originally designated a series unless otherwise provided with respect to
such series or tranche pursuant to a board resolution or a supplemental
indenture establishing such series or tranche.

            No reference herein to the Indenture and no provision of this [Note]
[Debenture] or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the Principal of and any
premium and interest on this [Note] [Debenture] in

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the manner, at the place, at the respective times, at the rate and in the coin
or currency herein prescribed.

            The [Notes] [Debentures] are issuable initially only in registered
form without coupons in denominations of [$1,000] or any integral multiple
thereof at the office or agency of the Company in the Borough of Manhattan, The
City of New York, and in the manner and subject to the limitations provided in
the Indenture.

            [This [Note] [Debenture] will not be redeemable at the option of the
Company prior to maturity.] [This [Note] [Debenture] is redeemable prior to
maturity _________.] [This Debenture is entitled to the benefits of a mandatory
sinking fund as follows: ___________.]

            Upon due presentment for registration of transfer of this [Note]
[Debenture] at the office or agency of the Company in the Borough of Manhattan,
The City of New York, a new [Note or Notes] [Debenture or Debentures] of
authorized denominations for an equal aggregate principal amount will be issued
to the transferee in exchange therefor, subject to the limitations provided in
the Indenture, without charge except for any tax or other governmental charge
imposed in connection therewith.

            The Company, the Trustee and any agent of the Company or the Trustee
may deem and treat the registered Holder hereof as the absolute owner of this
[Note] [Debenture] (whether or not this [Note] [Debenture] shall be overdue and
notwithstanding any notation of ownership or other writing hereon), for the
purpose of receiving payment of, or on account of, the Principal hereof and,
subject to the provisions hereof, interest hereon, and for all other purposes,
and neither the Company nor the Trustee nor any agent of the Company or the
Trustee shall be affected by any notice to the contrary.

            No recourse under or upon any obligation, covenant or agreement
contained in the Indenture or any indenture supplemental thereto or in any
[Note] [Debenture], or because of any indebtedness evidenced thereby, shall be
had against any incorporator as such, or against any past, present or future
stockholder, officer, director or employee, as such, of the Company or of any
successor, either directly or through the Company or any successor, under any
rule of law, statute or constitutional provision or by the enforcement of any
assessment or by any legal or equitable proceeding or otherwise, all such
liability being expressly waived and released by the acceptance hereof and as
part of the consideration for the issue hereof.

            Terms used herein which are defined in the Indenture shall have the
respective meanings assigned thereto in the Indenture.

            The laws of the State of New York (without regard to conflicts of
laws principles thereof) shall govern this [Note] [Debenture].

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            FOR VALUE RECEIVED, the undersigned hereby sell(s), assign(s) and
transfer(s) unto

[PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE]


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--------------------------------------------------------------------------------
[PLEASE PRINT OR TYPE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE]

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the within [Note] [Debenture] and all rights thereunder, hereby irrevocably
constituting and appointing
__________________________________________________________________Attorney to
transfer such [Note] [Debenture] on the books of the Issuer, with full power of
substitution in the premises.

                                   Signature:

Dated:
      ------------------           ---------------------------------------------
                                   NOTICE: The signature to this assignment must
                                   correspond with the name as written upon the
                                   face of the within [Note] [Debenture] in
                                   every particular without alteration or
                                   enlargement or any change whatsoever.

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