<PAGE>




                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 8-K

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

       Date of Report (Date of earliest event reported): October 27, 2005

                     VASCO DATA SECURITY INTERNATIONAL, INC.

               (Exact name of registrant as specified in charter)



       Delaware                   000-24389                 36-4169320
       --------                   ---------                 ----------
 (State or other juris-          (Commission              (IRS Employer
diction of incorporation)        File Number)           Identification No.)


1901 South Meyers Road, Suite 210
     Oakbrook Terrace, Illinois                                60181
----------------------------------------------                 -----
  (Address of principal executive offices)                   (Zip Code)


Registrant's telephone number, including area code:  (630) 932-8844



                                       N/A
          (Former name or former address, if changed since last report)


Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2. below):

[ ] Written communications pursuant to Rule 425 under the Securities Act
    (17 CFR 230.425)

[ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act
    (17 CFR 240.14a-12)

[ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the
    Exchange Act (17 CFR 240.14d-2(b))

[ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the
    Exchange Act (17 CFR 240.13e-4(c))


<PAGE>



ITEM 2.02 RESULTS OF OPERATIONS AND FINANCIAL CONDITION

On October 27, 2005, VASCO Data Security International, Inc. (VASCO) issued a
press release providing a financial update for the third quarter ended September
30, 2005. The full text of the press release is attached as Exhibit 99.1 to this
Current Report on Form 8-K.

On October 27, 2005, VASCO held a conference call with investors to discuss
VASCO's third quarter earnings and results of operations for the first nine
months of 2005. A script read by officers of VASCO during the conference call is
furnished as Exhibit 99.2 to this Current Report on Form 8-K.

The press release and the comments by VASCO during the conference call contained
a non-GAAP financial measure within the meaning of the Securities and Exchange
Commission's Regulation G. For purposes of Regulation G, a non-GAAP financial
measure is a numerical measure of a registrant's historical or future financial
performance, financial position or cash flows that excludes amounts, or is
subject to adjustments that have the effect of excluding amounts, that are
included in the most directly comparable measure calculated and presented in
accordance with GAAP in the statement of income, balance sheet or statement of
cash flows (or equivalent statements) of the issuer; or includes amounts, or is
subject to adjustments that have the effect of including amounts, that are
excluded from the most directly comparable measure so calculated and presented.

The press release contained a reference to EBITDA and provided a reconciliation
of EBITDA to net income (loss) on the face of the Consolidated Statement of
Operations. EBITDA is used by VASCO for comparisons to other companies within
its industry as an alternative to GAAP measures and is used by investors and
analysts in evaluating performance. EBITDA, which is earnings before interest,
taxes, depreciation and amortization, is computed by adding back net interest
expense, income tax expense, depreciation expense, and amortization expense to
net income as reported. EBITDA should be considered in addition to, but not as a
substitute for, other measures of financial performance reported in accordance
with accounting principles generally accepted in the United States. EBITDA, as
defined above, may not be comparable to similarly titled measures reported by
other companies.


ITEM 9.01 FINANCIAL STATEMENTS AND EXHIBITS

(c)      Exhibits

             Exhibit
             Number         Description
             ------         -----------

               99.1         Press release, dated October 27, 2005, providing
                            financial update of VASCO Data Security
                            International, Inc. for the third quarter ended
                            September 30, 2005.

               99.2         Text of script for October 27, 2005 Earnings
                            Conference Call.


<PAGE>

                                    SIGNATURE

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 hereunto duly authorized.



Date: October 27, 2005        VASCO Data Security International, Inc.
                              ---------------------------------------
                              (Registrant)



                              By: /s/Clifford K. Bown
                                  --------------------------------
                                  Clifford K. Bown
                                  Chief Financial Officer





<PAGE>



                                  EXHIBIT INDEX




             Exhibit No.    Description
             -----------    -----------

               99.1         Press release, dated October 27, 2005, announcing
                            financial update of VASCO Data Security
                            International, Inc. for the third quarter ended
                            September 30, 2005.

               99.2         Text of script for October 27, 2005 Earnings
                            Conference Call.
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SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 8-K

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

       Date of Report (Date of earliest event reported): October 27, 2005

                     VASCO DATA SECURITY INTERNATIONAL, INC.

               (Exact name of registrant as specified in charter)

       Delaware                   000-24389                 36-4169320
       --------                   ---------                 ----------
 (State or other juris-          (Commission              (IRS Employer
diction of incorporation)        File Number)           Identification No.)

1901 South Meyers Road, Suite 210
     Oakbrook Terrace, Illinois                                60181
----------------------------------------------                 -----
  (Address of principal executive offices)                   (Zip Code)

Registrant's telephone number, including area code:  (630) 932-8844

                                       N/A
          (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2. below):

[ ] Written communications pursuant to Rule 425 under the Securities Act
    (17 CFR 230.425)

[ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act
    (17 CFR 240.14a-12)

[ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the
    Exchange Act (17 CFR 240.14d-2(b))

[ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the
    Exchange Act (17 CFR 240.13e-4(c))
ITEM 2.02 RESULTS OF OPERATIONS AND FINANCIAL CONDITION

On October 27, 2005, VASCO Data Security International, Inc. (VASCO) issued a
press release providing a financial update for the third quarter ended September
30, 2005. The full text of the press release is attached as Exhibit 99.1 to this
Current Report on Form 8-K.

On October 27, 2005, VASCO held a conference call with investors to discuss
VASCO's third quarter earnings and results of operations for the first nine
months of 2005. A script read by officers of VASCO during the conference call is
furnished as Exhibit 99.2 to this Current Report on Form 8-K.

The press release and the comments by VASCO during the conference call contained
a non-GAAP financial measure within the meaning of the Securities and Exchange
Commission's Regulation G. For purposes of Regulation G, a non-GAAP financial
measure is a numerical measure of a registrant's historical or future financial
performance, financial position or cash flows that excludes amounts, or is
subject to adjustments that have the effect of excluding amounts, that are
included in the most directly comparable measure calculated and presented in
accordance with GAAP in the statement of income, balance sheet or statement of
cash flows (or equivalent statements) of the issuer; or includes amounts, or is
subject to adjustments that have the effect of including amounts, that are
excluded from the most directly comparable measure so calculated and presented.

The press release contained a reference to EBITDA and provided a reconciliation
of EBITDA to net income (loss) on the face of the Consolidated Statement of
Operations. EBITDA is used by VASCO for comparisons to other companies within
its industry as an alternative to GAAP measures and is used by investors and
analysts in evaluating performance. EBITDA, which is earnings before interest,
taxes, depreciation and amortization, is computed by adding back net interest
expense, income tax expense, depreciation expense, and amortization expense to
net income as reported. EBITDA should be considered in addition to, but not as a
substitute for, other measures of financial performance reported in accordance
with accounting principles generally accepted in the United States. EBITDA, as
defined above, may not be comparable to similarly titled measures reported by
other companies.

ITEM 9.01 FINANCIAL STATEMENTS AND EXHIBITS

(c)      Exhibits

             Exhibit
             Number         Description
             ------         -----------

               99.1         Press release, dated October 27, 2005, providing
                            financial update of VASCO Data Security
                            International, Inc. for the third quarter ended
                            September 30, 2005.

               99.2         Text of script for October 27, 2005 Earnings
                            Conference Call.
SIGNATURE

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 hereunto duly authorized.

Date: October 27, 2005        VASCO Data Security International, Inc.
                              ---------------------------------------
                              (Registrant)

                              By: /s/Clifford K. Bown
                                  --------------------------------
                                  Clifford K. Bown
                                  Chief Financial Officer
EXHIBIT INDEX

             Exhibit No.    Description
             -----------    -----------

               99.1         Press release, dated October 27, 2005, announcing
                            financial update of VASCO Data Security
                            International, Inc. for the third quarter ended
                            September 30, 2005.

               99.2         Text of script for October 27, 2005 Earnings
                            Conference Call.