<PAGE>   1

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                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                             ---------------------

                                  FORM 10-Q/A

            QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                        SECURITIES EXCHANGE ACT OF 1934
                             ---------------------

                      FOR THE QUARTER ENDED MARCH 31, 2001

                         COMMISSION FILE NUMBER 0-25016

                                 T-NETIX, INC.
             (Exact name of registrant as Specified in Its Charter)

<TABLE>
<S>                                            <C>
                  COLORADO                                      84-1037352
        (State of Other Jurisdiction                         (I.R.S. Employer
              of Incorporation)                             Identification No.)
</TABLE>

<TABLE>
<S>                                            <C>
           67 INVERNESS DRIVE EAST
             ENGLEWOOD, COLORADO                                   80112
   (Address of principal executive offices)                      (Zip Code)
</TABLE>

      Registrant's telephone number, including area code:  (303) 790-9111

                             ---------------------

       Securities registered pursuant to Section 12(b) of the Act: NONE.

    Securities registered pursuant to Section 12(g) of the Act:COMMON STOCK
                                                      (Title of Class)

     Indicate by check mark whether the Registrant: (1) has filed all reports to
be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.  Yes [X]  No [ ]

     Indicate the number of shares outstanding of each of the issuer's classes
of common stock, as of the latest practical date.

<TABLE>
<CAPTION>
                    CLASS                               OUTSTANDING AT MAY 10, 2001
                    -----                               ---------------------------
<S>                                            <C>
       Common stock, $0.01 stated value                          14,999,151
</TABLE>

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<PAGE>   2

                        FORM 10-Q CROSS REFERENCE INDEX

<TABLE>
<CAPTION>
                                                                       PAGE
                                                                       ----
<S>     <C>                                                            <C>
                       PART I FINANCIAL INFORMATION
Item 1  Condensed Financial Statements (Unaudited)..................     3
Item 2  Management's Discussion and Analysis of Financial Condition
          and Results of Operations.................................    11
Item 3  Quantitative and Qualitative Disclosure About Market Risk...    15

                         PART II OTHER INFORMATION
Item 1  Legal Proceedings...........................................    16
Item 2  Changes in Securities and Use of Proceeds...................    17
Item 3  Defaults Upon Senior Securities.............................    17
Item 4  Submission of Matters to a Vote of Security Holders.........    17
Item 5  Other Information...........................................    17
Item 6  Exhibits and Reports on Form 8-K............................    17
</TABLE>

                                        1
<PAGE>   3

                                     PART I

ITEM 1. FINANCIAL STATEMENTS

              INDEX TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

<TABLE>
<S>                                                           <C>
Condensed Consolidated Balance Sheets as of March 31, 2001
  and December 31, 2000 (Unaudited).........................    3
Condensed Consolidated Statements of Operations for the
  Three Months Ended March 31, 2001 and 2000 (Unaudited)....    4
Condensed Consolidated Statements of Cash Flows for the
  Three Months Ended March 31, 2001 and 2000 (Unaudited)....    5
Notes to Condensed Consolidated Financial Statements
  (Unaudited)...............................................    6
</TABLE>

                                        2
<PAGE>   4

                         T-NETIX, INC. AND SUBSIDIARIES

                     CONDENSED CONSOLIDATED BALANCE SHEETS
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
                                                               (AMOUNTS IN THOUSANDS)
<S>                                                           <C>         <C>
                                        ASSETS

Cash and cash equivalents...................................  $  1,099      $    102
Accounts receivable, net....................................    14,943        18,268
Prepaid expenses............................................     2,354         1,212
Inventories.................................................       613           764
                                                              --------      --------
          Total current assets..............................    19,009        20,346
Property and equipment, net.................................    35,736        34,821
Goodwill, net...............................................     5,345         5,557
Deferred tax asset..........................................     2,252         2,297
Intangible and other assets, net............................     8,190         8,474
                                                              --------      --------
          Total assets......................................  $ 70,532      $ 71,495
                                                              ========      ========

                         LIABILITIES AND STOCKHOLDERS' EQUITY

Liabilities:
  Accounts payable..........................................  $  7,494      $  8,654
  Accrued liabilities.......................................     7,507         5,781
  Current portion of long-term debt.........................    25,874         1,848
                                                              --------      --------
          Total current liabilities.........................    40,875        16,283
  Long-term debt............................................       141        26,063
  Subordinated note payable.................................     3,750         3,750
                                                              --------      --------
          Total liabilities.................................    44,766        46,096
Series A redeemable convertible preferred stock, $1,000 per
  share stated value, 3,750 shares authorized; 3,250 issued
  and outstanding at December 31, 2000......................        --         2,173
Stockholders' equity:
  Common stock, $.01 stated value, 70,000,000 shares
     authorized; 14,999,051 and 13,228,872 shares issued and
     outstanding at March 31, 2001 and December 31,
     respectively...........................................       150           132
  Additional paid-in capital................................    41,773        38,541
  Accumulated deficit.......................................   (16,157)      (15,447)
                                                              --------      --------
          Total stockholders' equity........................    25,766        23,226
                                                              --------      --------
Commitments and contingencies
          Total liabilities and stockholders' equity........  $ 70,532      $ 71,495
                                                              ========      ========
</TABLE>

     See accompanying notes to condensed consolidated financial statements.

                                        3
<PAGE>   5

                         T-NETIX, INC. AND SUBSIDIARIES

                CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                                THREE MONTHS ENDED
                                                                     MARCH 31,
                                                              -----------------------
                                                                2001          2000
                                                              ---------     ---------
                                                              (AMOUNTS IN THOUSANDS,
                                                                 EXCEPT PER SHARE
                                                                     AMOUNTS)
<S>                                                           <C>           <C>
Revenue:
  Telecommunications services...............................   $15,616       $10,125
  Direct call provisioning..................................     6,480         7,246
  Internet services.........................................     6,851         4,775
  Equipment sales and other.................................        86           382
                                                               -------       -------
          Total revenue.....................................    29,033        22,528
                                                               -------       -------
Expenses:
  Operating costs:
     Telecommunications services............................     6,074         4,501
     Direct call provisioning...............................     5,878         6,515
     Internet services......................................     4,916         4,057
     Cost of equipment sold and other.......................        41           218
                                                               -------       -------
          Total operating costs.............................    16,909        15,291
  Selling, general and administrative.......................     6,416         3,738
  Research and development..................................     1,481         1,175
  Depreciation and amortization.............................     3,150         3,049
                                                               -------       -------
          Total expenses....................................    27,956        23,253
                                                               -------       -------
          Operating income (loss)...........................     1,077          (725)
Interest and other income (expense), net....................      (710)         (354)
                                                               -------       -------
          Net income (loss).................................       367        (1,079)
Charge for conversion of redeemable convertible preferred
  stock.....................................................    (1,077)           --
                                                               -------       -------
Net income (loss) applicable to common shareholders.........   $  (710)      $(1,079)
                                                               =======       =======
Basic and diluted loss per common share.....................   $ (0.05)      $ (0.08)
                                                               =======       =======
Weighted average common shares..............................    14,288        12,715
                                                               =======       =======
</TABLE>

     See accompanying notes to condensed consolidated financial statements.

                                        4
<PAGE>   6

                         T-NETIX, INC. AND SUBSIDIARIES

                CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                              THREE MONTHS ENDED
                                                                   MARCH 31,
                                                              -------------------
                                                                2001       2000
                                                              --------   --------
                                                                  (AMOUNTS IN
                                                                  THOUSANDS)
<S>                                                           <C>        <C>
Cash flows from operating activities:
Net income (loss)...........................................  $   367    $(1,079)
Adjustments to reconcile net earnings to net cash provided
  by operating activities:
  Depreciation and amortization.............................    3,150      3,049
  Gain on sale of property and equipment....................       --       (248)
  Changes in operating assets and liabilities:
     Change in accounts receivable, net.....................    4,195      1,664
     Change in prepaid expenses.............................     (308)      (516)
     Change in inventory....................................      713       (610)
     Change in intangibles and other assets.................       67        (16)
     Change in accounts payable.............................   (1,292)      (222)
     Change in accrued liabilities..........................      178       (612)
                                                              -------    -------
          Cash provided by operating activities.............    7,070      2,630
                                                              -------    -------
Cash used in investing activities:
  Purchase of property and equipment........................   (2,561)    (5,046)
  Purchase of Telequip, Inc. ...............................   (1,477)        --
  Proceeds from disposal or property and equipment..........       --        228
  Other investing activities................................       --         (9)
                                                              -------    -------
          Cash used in investing activities.................   (4,038)    (4,827)
                                                              -------    -------
Cash flows from financing activities:
  Net proceeds (payments) under line of credit..............   (2,022)     2,351
  Payments of other debt....................................      (13)      (161)
  Common stock issued for cash under option plans...........       --         67
                                                              -------    -------
          Cash provided by (used in) financing activities...   (2,035)     2,257
                                                              -------    -------
Net increase (decrease) in cash and cash equivalents........      997         60
Cash and cash equivalents at beginning of period............      102        118
                                                              -------    -------
Cash and cash equivalents at end of period..................  $ 1,099    $   178
                                                              =======    =======
Cash paid for interest......................................  $   748    $   638
                                                              =======    =======
Cash paid for income taxes..................................  $    --    $    --
                                                              =======    =======
</TABLE>

     See accompanying notes to condensed consolidated financial statements.

                                        5
<PAGE>   7

                         T-NETIX, INC. AND SUBSIDIARIES

              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                  (UNAUDITED)

(1) SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

  Unaudited Financial Statements

     The accompanying unaudited consolidated financial statements reflect all
adjustments which, in the opinion of management, are necessary to reflect a fair
presentation of the financial position and results of operations of T-NETIX,
Inc. and subsidiaries (the Company) for the interim periods presented. All
adjustments, in the opinion of management, are of a normal and recurring nature.
Some adjustments involve estimates, which may require revision in subsequent
interim periods or at year-end. The financial statements have been presented in
accordance with generally accepted accounting principles. Refer to notes to
consolidated financial statements, which appear in the 2000 Annual Report on
Form 10-K for the Company's accounting policies, which are pertinent to these
statements.

     Certain amounts in the 2000 financial statements have been reclassified to
conform to the 2001 presentation.

  Acquisitions

     On January 19, 2001 the Company completed the purchase of all the
outstanding shares of common stock, not already owned, of Telequip Labs, Inc., a
provider of telecommunications calling services. The purchase price was $605 per
share of which $573 per share was paid upon closing. The remaining $32 per share
is payable on the first anniversary of the closing date upon determination that
all representations and warranties were materially true and accurate as of the
closing date and all covenants have been substantially fulfilled. The excess of
the purchase price over the fair value of the net identifiable assets acquired
has been recorded as goodwill and is being amortized on a straight line basis
over seven years. Total cash paid in January was $1.5 million. The acquisition
is being accounted for as a purchase and accordingly, the results of operations
of Telequip Labs, Inc. have been included in the Company's consolidated
financial statements from January 19, 2001.

  Earnings (Loss) Per Common Share

     Earnings (loss) per common share are presented in accordance with the
provisions of Statement of Financial Accounting Standards No. 128, Earnings Per
Share (SFAS 128). Basic earnings per share excludes dilution for common stock
equivalents and is computed by dividing income or loss available to common
shareholders by the weighted average number of common shares outstanding during
the period. Diluted earnings per share reflect the potential dilution that could
occur if securities or other contracts to issue common stock were exercised or
converted into common stock. For the three months ended March 31, 2001 and 2000,
common stock equivalents of 61,000 and 495,000 respectively were not included in
the diluted earnings per share calculation, as their effect would be
anti-dilutive.

                                        6
<PAGE>   8
                         T-NETIX, INC. AND SUBSIDIARIES

      NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)

(2) BALANCE SHEET COMPONENTS

     Accounts receivable consist of the following:

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
                                                               (AMOUNTS IN THOUSANDS)
<S>                                                           <C>         <C>
Accounts receivable, net:
  Trade accounts receivable.................................   $ 9,770      $13,216
  Direct call provisioning receivables......................     5,800        5,934
  Other receivables.........................................       421          209
                                                               -------      -------
                                                                15,991       19,359
          Less: Allowance for doubtful accounts.............    (1,048)      (1,091)
                                                               -------      -------
                                                               $14,943      $18,268
                                                               =======      =======
</TABLE>

     Bad debt expense was $1,235,000 and $1,351,000 for the three months ended
March 31, 2001 and 2000, respectively.

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
                                                               (AMOUNTS IN THOUSANDS)
<S>                                                           <C>         <C>
Property and equipment, net:
  Telecommunications equipment..............................   $64,140      $62,833
  Construction in progress..................................     8,024        6,495
  Office equipment..........................................    13,359       11,544
                                                               -------      -------
                                                                85,523       80,872
          Less: Accumulated depreciation and amortization...   (49,787)     (46,051)
                                                               -------      -------
                                                               $35,736      $34,821
                                                               =======      =======
</TABLE>

     Intangible and other assets consist of the following:

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
                                                               (AMOUNTS IN THOUSANDS)
<S>                                                           <C>         <C>
Intangible and other assets, net:
  Patent license rights.....................................   $ 3,325      $ 3,325
  Purchased technology assets...............................     2,487        2,487
  Capitalized software development costs....................       663          633
  Acquired software technologies............................     1,809        1,809
  Patent defense and application costs......................     2,919        2,915
  Deposits and long-term prepayments........................     1,827        1,718
  Other.....................................................     1,366        1,500
                                                               -------      -------
                                                                14,396       14,387
  Less: Accumulated amortization............................    (6,206)      (5,913)
                                                               -------      -------
                                                               $ 8,190      $ 8,474
                                                               =======      =======
</TABLE>

                                        7
<PAGE>   9
                         T-NETIX, INC. AND SUBSIDIARIES

      NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)

(2) BALANCE SHEET COMPONENTS -- (CONTINUED)

     Accrued liabilities consist of the following:

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
                                                               (AMOUNTS IN THOUSANDS)
<S>                                                           <C>         <C>
Accrued liabilities:
  Deferred revenue and customer advances....................   $1,969        $1,905
  Compensation related......................................    1,589         1,281
  Other.....................................................    3,949         2,595
                                                               ------        ------
                                                               $7,507        $5,781
                                                               ======        ======
</TABLE>

(3) DEBT

     Debt consists of the following:

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
                                                               (AMOUNTS IN THOUSANDS)
<S>                                                           <C>         <C>
Debt:
  Bank lines of credit......................................   $25,821      $27,813
  Subordinated note payable.................................     3,750        3,750
  Other.....................................................       194           98
                                                               -------      -------
                                                                29,765       31,661
  Less current portion......................................    25,874        1,848
                                                               -------      -------
          Non current portion...............................   $ 3,891      $29,813
                                                               =======      =======
</TABLE>

     In September 1999, the Company entered into a Senior Secured Revolving
Credit Facility (the "Credit Facility") with its commercial bank. In April 2001,
The Company's lenders extended the maturity date on its credit agreement to
March 31, 2002. The maximum available borrowings in the facility was reduced to
$30 million and interest was set at prime rate plus 1.25% effective March 31,
2001 increasing by 0.25% each quarter thereafter on June 30, September 30 and
December 31, 2001. The Company also pays a fee of 0.40% per annum on the unused
portion of the line of credit.

     The Credit Facility is collateralized by substantially all of the assets of
the Company. Under the terms of the Credit Facility, the Company is required to
maintain certain financial ratios and other financial covenants. These ratios
include a debt to a four quarter rolling earnings before interest, taxes and
depreciation and amortization (EBITDA) ratio, a ratio of fixed charges (interest
and debt payments) to EBITDA, and minimum quarterly EBITDA. The Agreement also
prohibits the Company from incurring additional indebtedness.

     The Company issued a subordinated note payable for $3.75 million, due April
30, 2001, to a director and significant shareholder of the Company. The note
bears interest at prime rate plus one percent per annum (8.75% at March 31,
2001) which is payable every six months. The lender received warrants, which are
immediately exercisable, to purchase 25,000 shares of common stock at an
exercise price of $6.05 per share for a period of five years. The estimated fair
value of the stock purchase warrants, calculate using the Black-Scholes model,
has been recorded as deferred financing fees and is being amortized over the
term of the debt. This note was extended in April 2001, to April 30, 2002.

                                        8
<PAGE>   10
                         T-NETIX, INC. AND SUBSIDIARIES

      NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)

(4) SEGMENT INFORMATION

     The Company has three reportable segments; the Corrections Divisions, the
SpeakEZ Division, and Internet Services Division. The Company evaluates
performance based on earnings (loss) before income taxes. Additional measures
include operating income, depreciation and amortization, and interest expense.
There are no intersegment sales. The Company's reportable segments are specific
business units that offer different products and services. They are managed
separately because each business requires different technology and marketing
strategies. The accounting policies of the reportable segments are the same as
those described in the summary of significant accounting policies. Segment
information for the three months ended March 31, 2001 and 2000 is as follows
(amounts in thousands):

<TABLE>
<CAPTION>
                                                               2001      2000
                                                              -------   -------
<S>                                                           <C>       <C>
REVENUE FROM EXTERNAL CUSTOMERS:
  Corrections Division......................................  $22,154   $17,672
  SpeakEZ Division..........................................       28        81
  Internet Services Division................................    6,851     4,775
                                                              -------   -------
                                                              $29,033   $22,528
                                                              =======   =======
OPERATING INCOME (LOSS):
  Corrections Division......................................  $  (181)  $(1,053)
  SpeakEZ Division..........................................     (677)     (390)
  Internet Services Division................................    1,935       718
                                                              -------   -------
                                                              $ 1,077   $  (725)
                                                              =======   =======
RESEARCH AND DEVELOPMENT
  Corrections Division......................................  $ 1,335   $   946
  SpeakEZ Division..........................................      146       103
  Internet Services Division................................       --        --
                                                              -------   -------
                                                              $ 1,481   $ 1,175
                                                              =======   =======
DEPRECIATION AND AMORTIZATION
  Corrections Division......................................  $ 2,948   $ 2,812
  SpeakEZ Division..........................................      202       237
  Internet Services Division................................       --        --
                                                              -------   -------
                                                              $ 3,150   $ 3,049
                                                              =======   =======
INTEREST AND OTHER INCOME (EXPENSE)
  Corrections Division......................................  $  (380)  $   (76)
  SpeakEZ Division..........................................     (330)     (278)
  Internet Services Division................................       --        --
                                                              -------   -------
                                                              $  (710)  $  (354)
                                                              =======   =======
SEGMENT EARNINGS (LOSS) BEFORE TAX:
  Corrections Division......................................  $  (561)  $(1,129)
  SpeakEZ Division..........................................   (1,007)     (668)
  Internet Services Division................................    1,935       718
                                                              -------   -------
                                                              $   367   $(1,079)
                                                              =======   =======
</TABLE>

                                        9
<PAGE>   11
                         T-NETIX, INC. AND SUBSIDIARIES

      NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)

(4) SEGMENT INFORMATION -- (CONTINUED)

<TABLE>
<CAPTION>
                                                              MARCH 31,   DECEMBER 31,
                                                                2001          2000
                                                              ---------   ------------
<S>                                                           <C>         <C>
SEGMENT ASSETS:
Corrections Division........................................   $68,931      $69,676
SpeakEZ Division............................................     1,601        1,819
Internet Services Division..................................        --           --
                                                               -------      -------
                                                               $70,532      $71,495
                                                               =======      =======
</TABLE>

     There was no intersegment revenue for the three months ended March 31, 2001
and 2000. Consolidated total assets included eliminations of approximately $14.1
million and $13.2 million as of March 31, 2001 and December 31, 2000,
respectively. Eliminations consist of intercompany receivables in the
Corrections Division and intercompany payables in the SpeakEZ Division related
solely to intercompany borrowing of the SpeakEZ Division.

                                        10
<PAGE>   12

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
OF OPERATIONS

     For a comprehensive understanding of our financial condition and
performance, this discussion should be considered within the context of the
consolidated financial statements and accompanying notes and other information
contained herein.

     The Private Securities Litigation Reform Act of 1995 provides a "safe
harbor" for forward-looking statements. Certain information contained in this
Management's Discussion and Analysis of Financial Condition and Results of
Operations and elsewhere in this Form 10-K includes forward-looking statements.
Important factors that could cause actual results to differ materially from
those in the forward-looking statements include, but are not limited to, those
listed under the caption "Risk Factors," which may affect the potential
technological obsolescence of existing systems, the renewal of existing site
specific Corrections and Internet Service Division customer contracts, the
ability to retain the base of current site specific customer contracts, the
continued relationship with existing customers, the ability to win new contracts
for our products and services, including Lock & Track(TM), Contain(R) and the
Internet Services Division, the successful integration of Gateway Technologies,
Inc. into our business, our ability to penetrate the market for jail management
systems, the ability to reduce expenditures in the SpeakEZ Division and to
successfully license voice verification and fraud prevention technology, the
effect of economic conditions, the effect of regulation, including the
Telecommunications Act of 1996 that could affect our sales or pricing, the
impact of competitive products and pricing particularly in the our Corrections
Division, our continuing ability to develop hardware and software products,
commercialization and technological difficulties, manufacturing capacity and
product supply constraints or difficulties, actual purchases by current and
prospective customers under existing and expected agreements, and the results of
financing efforts, along with the other risks detailed herein.

OVERVIEW

  Corrections Division

     In the Corrections Division we derive revenue from three main sources:
telecommunications services, direct call provisioning and equipment sales. Each
form of revenue has specific and varying operating costs associated with such
revenue. Selling, general and administrative expenses, along with research and
development and depreciation and amortization are common expenses regardless of
the revenue generated.

     Telecommunications services revenue is generated under long-term contracts,
which provide for transaction fees paid on a per-call basis or fees based on a
percentage of revenue. The per-call charge is primarily for the provisioning of
specialized call processing services to telecommunications service providers for
their customers, the correctional facilities. Such telecommunications service
providers include AT&T, Bell Atlantic, US WEST, SBC Communications (including
Ameritech), BellSouth, Sprint and GTE, and other telecommunications service
providers. In transaction fee arrangements, we are paid a prescribed fee for
each call completed and additional fees for validating phone numbers dialed by
inmates.

     As a direct inmate call provider, we buy "wholesale" call services to be
re-sold as collect calls. We use the services of third parties to bill the
collect calls. We then enter into direct contracts with the correctional
facilities and generally pay to the correctional facilities commissions on the
gross billed revenue. The rates charged by us are consistent with the collect
call rates charged by the incumbent local exchange carrier or "ILEC" in the same
service area and the predominant interexchange carrier or "IXC." Since all calls
originating from the inmate phones are collect calls, each phone generates
higher-than-industry-average revenues. The uncertainty of the creditworthiness
of the billed parties results however in a higher-than-industry-average
uncollectible cost.

     Equipment sales and other revenue includes the sales of our inmate calling
system and the DRS system. The sales of the inmate calling system are generally
made to only one customer. We then charge monthly maintenance fees to keep the
system operational. Sales to this customer can vary depending upon the success
of the customer in winning contracts with correctional facilities.

                                        11
<PAGE>   13

  Internet Services Division

     In December 1999, we entered into a master service agreement with US WEST
!NTERPRISE (now named Qwest) America, Inc. to provide interLATA Internet
services to Qwest customers. The contract, which commenced December 1, 1999,
called for us to buy, resell and process billing of Internet bandwidth to this
customer. The contract with Qwest was for a minimum of sixteen months.

     Factors affecting margin include a negotiated base management fee and
contract incentive payments based on cost savings. The costs associated with
this contract are primarily the costs for Internet bandwidth. There were no
capital outlays required to begin provisioning these services.

     Upon expiration of the initial period in March 2001, we are continuing to
provide service on a month-to-month basis. At the conclusion of the contract, we
anticipate that these services will be discontinued .

  Speaker Verification Division

     We completed consolidation of our SpeakEZ operations to our Englewood
facility in February 1999. The reorganization at that time included a change in
marketing strategy from a direct customer sales strategy to a technology
licensing strategy. Our voice print revenue has been minimal to date and
management is seeking strategic alternatives including the sale of this
division. In the meantime this division will continue to incur its normal
operating expenses. There is no assurance that the SpeakEZ products will be
commercially accepted or profitable in the future and there is no assurance that
we will be able to sell or otherwise divest of this operation.

RESULTS OF OPERATIONS

     The following table sets forth certain statement of operations data as a
percentage of total revenue for the three months ended March 31, 2001 and 2000.

<TABLE>
<CAPTION>
                                                              2001   2000
                                                              ----   ----
<S>                                                           <C>    <C>
Revenue:
  Telecommunications services...............................   52%    43%
  Direct call provisioning..................................   22     31
  Internet services.........................................   24     25
  Equipment sales and other.................................    2      1
                                                              ---    ---
          Total revenue.....................................  100    100
Expenses:
  Operating costs...........................................   58     69
  Selling, general and administrative.......................   22     16
  Research and development..................................    5      5
  Depreciation and amortization.............................   11     13
                                                              ---    ---
          Operating loss....................................    4     (3)
  Interest and other income (expense), net..................   (2)    (2)
                                                              ---    ---
          Net income (loss).................................    2%    (5)%
                                                              ===    ===
</TABLE>

     Total Revenue.  Total revenue for the three months ended March 31, 2001 was
$29 million, an increase of 29% over $22.5 million for the corresponding prior
period. This increase was primarily attributable to the increase of
approximately $2.1 million in internet services, as well as an increase of
approximately $5.1 million in telecommunications services revenue offset by a
decrease in direct call provisioning revenue of approximately $0.7 million.

     The 50% increase in telecommunications services revenue to $15.6 million in
the three months ended March 31, 2001, from $10.1 million for the corresponding
prior period, was due primarily to new pricing agreements with four of our major
partners in the second half of 2000 and to a lesser degree increases in call
volumes, primarily due to the addition of new sites.

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<PAGE>   14

     Direct call provisioning revenue decreased to $6.5 million for the three
months ended March 31, 2001, from $7.2 million in the corresponding prior
period. This decrease was due to the loss of sites for which we are provisioning
the long distance service.

     The Internet Services contract which commenced in December 1999 provided
revenues of approximately $6.9 million for the three months ended March 31, 2001
compared to $4.8 million for the comparable period in 2000 an increase of
approximately 43% due to and increase in the number of customers being served.
This contract expired on March 31, 2001, and although we anticipate incurring
month-to-month revenues through September 2001, we anticipate operations of this
division to cease at such time.

     Equipment sales and other revenue decreased to $86,000 for the three months
ended March 31, 2001 from $382,000 in the corresponding prior period. Such sales
are primarily associated with one telecommunications service provider customer
and are dependent upon the timing of installations for this customer and the
customer's success rate in its territory. The decrease for the three months
ended March 31, 2001 from the corresponding prior period is due primarily to the
timing of purchases from this customer.

     Operating costs.  Total operating costs were $16.9 million in the three
months ended March 31, 2001, an increase of 10% from $15.3 million in the
corresponding prior period. The increases were primarily due to increases in
telecommunication services and internet services expenses, offset by a reduction
in direct call provisioning expenses and the cost of equipment sold and other
expenses.

     Operating costs of telecommunications services primarily consist of service
administration costs for correctional facilities, including salaries and related
personnel expenses, communication costs and inmate calling systems repair and
maintenance expense. Operating costs of telecommunications services also include
costs associated with call verification procedures, primarily network expenses
and database access charges. Operating costs associated with direct call
provisioning include the costs associated with telephone line access, long
distance charges, commissions paid to correctional facilities, costs associated
with uncollectible accounts and billing charges.. Internet Services expense
consists of Internet bandwidth costs. Cost of equipment sold and other includes
the purchase price of equipment which is resold. Other equipment cost components
were minimal.

     The following table sets forth the operating costs and expenses for each
type of revenue as a percentage of corresponding revenue for the three months
ended March 31, 2001 and 2000.

<TABLE>
<CAPTION>
                                                              2001   2000
                                                              ----   ----
<S>                                                           <C>    <C>
Operating costs:
  Telecommunications services...............................   40%    44%
  Direct call provisioning..................................   91     90
  Internet services.........................................   72     85
  Cost of equipment sold and other..........................    9     57
</TABLE>

     Operating costs associated with providing telecommunications services as a
percentage of corresponding revenue was 40% for the three months ended March 31,
2001, a decrease from 44% for the corresponding prior period. The percentage
decrease was due to revenue increases due to new pricing arrangements without
the same level of increases in telecommunications services operating expenses.
Total telecommunications services operating expenses were $6.1 million for the
three months ended March 31, 2000 and $4.5 million for the corresponding prior
period. The increase in 2001 is due to increases in communications expenses that
previously were passed through to our partners under old pricing agreements,
increased contract labor costs and higher travel related expenses. We anticipate
that we will continue to increase our personnel costs for our National Service
Center and other operations management personnel, however, we believe this
centralization of customer support will allow us to continue to reduce field
operations costs.

     Direct call provisioning costs as a percentage of applicable revenue
increased to 91% of revenue for the three months ended March 31, 2000 from 90%
for the corresponding prior period. Although there was a slight increase in
direct call provisioning as a percent of revenues, there was a decrease in
direct call provisioning expense of $637,000 due primarily to a reduction in
revenues and related direct expenses. In addition,

                                        13
<PAGE>   15


decreased as a percentage of revenues because of negotiated lower long distance
pricing from our vendors.

     Internet services expense increased due to increased number of customers
using the service and the related direct bandwidth costs needed to provide these
services. These bandwidth charges decreased as a percentage of sales as a result
of increased cost savings initiatives taken by the Company.

     Selling, General and Administrative Expenses.  Selling, general and
administrative expenses were $6.4 million for the three months ended March 31,
2001 compared to $3.7 million for the corresponding prior period. The increase
in the three months ended March 31, 2000 was primarily due to increases in
salary and benefits for additional sales personnel and from raises and cost of
living adjustments for existing personnel. Other increased costs were incurred
for travel and related expenses, communications cost, consulting fees, and legal
fees.

     Research and Development Expenses.  Research and development expenses were
$1.5 million in the three months ended March 31, 2001 compared to $1.2 million
for the corresponding prior period. Research and development expenses for the
Corrections Division were $1.3 million in the three months ended March 31, 2001
and $1.0 million in the corresponding prior period. The increase was primarily
due to higher personnel expenses.

     Depreciation and Amortization Expenses.  Depreciation and amortization
expense was $3.2 million in the three months ended March 31, 2001, an increase
from $3.0 million for the corresponding prior period. The increase was due
primarily to the depreciation associated with new site installations and
additional computer equipment and software purchased for internal use.

     Interest and Other Income (Expense), Net.  Interest and other income
(expense), net was $710,000 for the three months ended March 31, 2001, an
increase from $354,000 for the corresponding prior period. Included in other
income in the three months ended March 31, 2000 is a gain of approximately
$248,000 on the sale of used telecommunications equipment. Interest expense was
$714,000 for the three months ended March 31, 2001, and $641,000 for the
corresponding prior period. The increase in 2001 was attributable to an increase
in the average interest rate on outstanding indebtedness.

LIQUIDITY AND CAPITAL RESOURCES

  Cash Flows

     We have historically relied upon operating cash flow, debt financing and
the sale of equity securities to fund our operations and capital needs. Our
capital needs consist primarily of additions to property and equipment for site
telecommunication equipment and internal equipment requirements.

     Cash Provided by operations increased by 169% to $7.1 million for the three
months ended March 31, 2001 from $2.6 million in the comparable period in 2000.
This increase was primarily due to reductions in accounts receivable offset
somewhat by decreases in accounts payable.

     We anticipate that our capital expenditures in 2001 will decrease compared
with 2000 based on our anticipated growth in installed systems at correctional
facilities. We believe our cash flows from operations and our availability under
our credit facility will be sufficient in order for us to meet our anticipated
cash needs for new installations of inmate call processing systems and upgrades
of existing systems and to finance our operations for at least the next 12
months.

     Cash used in investing activities consisted primarily of purchases of
property and equipment of $2.6 million in 2001 compared to $5 million in 2000.
The decrease in 2000 was the result of a decrease in calling system
installations compared to 2000. Cash used for acquisitions amounted to $1.5
million in 2001.

     Cash used in financing consisted primarily of net payments on the Company's
credit facility of $2 million in 2001, and net borrowings on the credit facility
of $2.4 million in 2000.

                                        14
<PAGE>   16

  Capital Resources

     In September 1999, we entered into a Senior Secured Revolving Credit
Facility ("Credit Facility") with a commercial bank. In July 2000 our lenders
amended our credit agreement to revise certain financial covenants. The maximum
available amount of credit under the credit facility available to us is
dependent upon our financial performance. Based on the financial covenants, our
maximum borrowings at December 31, 2000 were $40.0 million. In April 2001 our
lenders extended the Credit Facility maturity date to March 31, 2002. The
maximum available borrowing on the facility was reduced to $30 million
consisting of a $10 million term portion and a $20 million line of credit.
Interest was set at prime rate plus 1.25% effective March 31, 2001, increasing
by 0.25% each quarter thereafter on June 30, September 30, and December 31,
2001. In addition, monthly payments of $200,000 on the term loan will commence
on April 30, 2001.

     In April 2000, we raised $7.5 million of debt and equity financing. The net
proceeds of approximately $7.2 million were used to reduce the outstanding
balance on the Credit Facility. The Company issued 3,750 shares of series A
non-voting redeemable convertible preferred stock and five-year stock purchase
warrants to acquire 340,909 common shares for net proceeds of $3.5 million. In
February of 2001 the remaining 3,250 shares of preferred stock were converted
into 1,770,179 shares of common stock at an average conversion price of $1.95
per common share. The unamortized discount on the preferred stock of $1.1
million was recognized as a charge to income (loss) applicable to common
stockholders. In April 2000, we also issued subordinated debt in the amount of
$3.75 million which is payable to a director and significant shareholder. The
maturity date of this note has been extended to April 30, 2002.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURE ABOUT MARKET RISK

     We are exposed to interest rate risk as discussed below.

INTEREST RATE RISK

     We have current debt outstanding under a line of credit of $25.8 million at
March 31, 2001. The loan bears interest at prime rate plus 1.25% (9.0% at March
31, 2001). Interest is payable monthly. Since the interest rates on the loans
outstanding are variable and are reset periodically, we are exposed to interest
rate risk. An increase in interest rates of 1% would increase estimated annual
interest expense by approximately $258,000 based on the amount of borrowings
outstanding under the line of credit at March 31, 2001.

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<PAGE>   17

                                    PART II

                               OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

     From time to time we have been, and expect to continue to be subject to
various legal and administrative proceedings or claims in the normal course of
our business. We believe the ultimate disposition of these matters will not have
a material affect on our financial condition, liquidity, or results of
operations.

     Last year Gateway won a dismissal of a case brought in the First Judicial
District Court of the State of New Mexico, styled Valdez v. State of New Mexico,
et al. An appeal of the case was recently certified and the case is currently in
the appellate briefing phase. The case named as defendants the State of New
Mexico, several political subdivisions of the State of New Mexico, and several
inmate telecommunications service providers, including Gateway. The complaint
included a request for certification by the court of a plaintiffs' class action
consisting of all persons who had been billed for and paid for telephone calls
initiated by an inmate confined in a jail, prison, detention center or other New
Mexico correctional facility. The complaint alleged violations of New
Mexico Unfair Practices Act, the New Mexico Antitrust Act and the New Mexico
Constitution, and also alleged unjust enrichment, constructive trust, economic
compulsion, constructive fraud and illegality of contracts, all in connection
with the provision of "collect only" inmate telecommunications services. The
case was never certified as a class action.

     T-NETIX is a defendant in another state case brought in the Superior Court
of Washington for King County, styled Sandy Judd, et al. v. American Telephone
and Telegraph Company, et al. In this case, the complaint joined several inmate
telecommunications service providers as defendants, including T-NETIX. The
complaint includes a request for certification by the court of a plaintiffs'
class action consisting of all persons who have been billed for and paid for
telephone calls initiated by an inmate confined in a jail, prison, detention
center or other Washington correctional facility. The complaint alleges
violations of the Washington Consumer Protection Act (WCPA) and requests an
injunction under the Washington Consumer Protection Act and common law to enjoin
further violations. The trial court has dismissed all claims with prejudice
against all defendants except T-NETIX and AT&T. These claims have been referred
to the Washington Utilities and Transportation Commission while the trial court
proceeding is in abeyance.

     Gateway is presently included in an appeal from a favorable ruling in
Kentucky federal court in the case Gus "Skip" Daleure, Jr., et al vs.
Commonwealth of Kentucky, et al. The complaint in this case joined as defendants
several states, political subdivisions of states, and inmate service
telecommunications providers and was filed contemporaneously with a request for
certification by the court of a nationwide plaintiffs' class action consisting
of all persons who have received and paid for telephone calls initiated by an
inmate at a prison, jail or other correctional institution for the provision of
"collect only" inmate telecommunications services. The complaint sought
declaratory and injunctive relief and money damages in an unstated amount for
alleged violations of the Sherman Antitrust Act, the Robinson-Patman Act and the
U.S. Constitution. The district court held, on motions to dismiss, that Kentucky
did not have personal jurisdiction over defendants not located in or doing
business in the state of Kentucky; that telephone calls are not goods or
commodities and thus are not subject to the antitrust provisions of the
Robinson-Patman Act; that Plaintiffs did not state a claim for relief under the
Equal Protection Clause of the Fourteenth Amendment; and that Plaintiffs had not
shown any harm in support of its antitrust claim under Section 1 of the Sherman
Act. The trial judge did not, however, dismiss the plaintiff's prayer for
injunctive relief, despite these findings. The case is currently subject to
appeal and cross appeal in the Second Circuit Court of Appeals. Although Gateway
believes the District Court holding will not be overturned, it is possible that
it may be, and there can be no assurance that a judgment against a class of the
providers will not ultimately be entered.

     In another case styled Robert E. Lee Jones, Jr. vs. MCI Communications, et
al, plaintiffs, 43 inmates of the Bland Correctional Center in Virginia, filed a
pro se action alleging constitutional violations, RICO Act violations and
violations of Federal wiretapping laws. Plaintiff's motion for certification for
a class action was denied and T-NETIX and MCI have filed Motions to Dismiss.
Pleadings are still being submitted in this case.
                                        16
<PAGE>   18

     In February, 2001 a case styled Mildred Fair, et al vs. Sprint Payphone
Services, et al was filed by four relatives of inmates of an unnamed South
Carolina correctional institution. The case was initially filed in state court
but was removed to Federal court. Defendants, in addition to T-NETIX, include
AT&T, BellSouth, GTE, Sprint United, Rock Hill Telephone Company, the South
Carolina Department of Corrections and the State of South Carolina. Plaintiffs'
claims include violations of the South Carolina Antitrust Act and the South
Carolina Unfair Trade Practices Act, unjust enrichment, constructive fraud and
unlawful taking under the South Carolina constitution. This case is in its very
early stage and answers and responsive pleadings by the various parties are
being prepared and submitted.

     We believe the ultimate disposition of the forgoing matters will not have a
material affect on our financial condition, liquidity, or results of operations.

ITEM 2. CHANGES IN SECURITIES AND USE OF PROCEEDS

     None

ITEM 3. DEFAULTS UPON SENIOR SECURITIES

     None.

ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

     None.

ITEM 5. OTHER INFORMATION

     None.

ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

                                        17
<PAGE>   19

                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                            T-NETIX, INC.
                                            (Registrant)

                                            By:    /s/ THOMAS E. LARKIN
                                              ----------------------------------
                                                       Thomas E. Larkin
                                                   Chief Executive Officer

Date May 15, 2001

                                        18