Exhibit 99.1 PRO FORMA FINANCIAL INFORMATION INDEX PAGE ---- Description of Pro Forma Financial Information........................... P-2 Unaudited Pro Forma Consolidated Condensed Statement of Operations for the Year ended December 31, 1999........................................ P-3 Notes to Unaudited Pro Forma Financial Information....................... P-4 P-1 PRO FORMA FINANCIAL INFORMATION The accompanying pro forma financial information gives effect to the September 1999 acquisition of Atcom, Inc. for approximately $42.6 million in common stock, stock options and direct acquisition costs as if such transaction had been consummated on January 1, 1999. The Atcom, Inc. acquisition was accounted for under the purchase method of accounting for business combinations. The pro forma consolidated condensed financial information does not include the effects of the acquisition of Business Anywhere USA, Inc. as the impact of the acquisition is not significant to the consolidated condensed pro forma results for the period presented. The pro forma consolidated condensed financial information is presented for illustrative purposes only and is not necessarily indicative of what CAIS Internet, Inc.'s results of operations would have been had the above-referenced transaction been consummated as of the above-referenced date or results of operations that may be reported by CAIS Internet, Inc. in the future. The pro forma adjustments are based upon available information and, in the opinion of management, all adjustments have been made that are necessary to present fairly the pro forma data. The following data should be read in conjunction with CAIS Internet, Inc.'s and Atcom, Inc.'s Consolidated Financial Statements and related notes included in CAIS Internet, Inc.'s filings with the Securities and Exchange Commission. P-2 CAIS INTERNET, INC. UNAUDITED PRO FORMA CONSOLIDATED CONDENSED STATEMENT OF OPERATIONS For the Year Ended December 31, 1999 (in thousands, except per share amounts) Historical Results ------------------------------- Atcom (Through Date of Pro Forma Pro Forma CAIS Internet Acquisition Only) Adjustments CAIS Internet ------------- ----------------- ----------- ------------- Net revenues............ $ 10,784 $ 1,202 $ 11,986 Cost of revenues........ 9,689 461 10,150 Operating expenses: Selling, general and administrative....... 39,693 3,002 42,695 Research and development.......... 1,593 604 2,197 Depreciation and amortization......... 7,666 46 $ 9,307(1) 17,019 Fair value of stock issued to third party for services......... 723 -- 723 Non-cash compensation......... 4,892 -- 4,892 -------- ------- ------- -------- Total operating expenses........... 54,567 3,652 9,307 67,526 -------- ------- ------- -------- Loss from operations.... (53,472) (2,911) (9,307) (65,690) Interest income (expense), net: Interest income....... 2,419 37 2,456 Interest expense...... (1,384) (136) (1,520) -------- ------- ------- -------- Total interest income (expense), net..... 1,035 (99) -- 936 -------- ------- ------- -------- Loss from continuing operations before income taxes ... (52,437) (3,010) (9,307) (64,754) Provision for income taxes................ -- -- -- -------- ------- ------- -------- Loss from continuing operations............. (52,437) (3,010) (9,307) (64,754) Loss from discontinued operations........... (340) -- (340) -------- ------- ------- -------- Loss before extraordinary item..... (52,777) (3,010) (9,307) (65,094) Extraordinary item-- early extinguishment of debt.............. (551) -- (551) -------- ------- ------- -------- Net loss................ (53,328) (3,010) (9,307) (65,645) Dividends and accretion of preferred stock...... (4,520) -- (4,520) -------- ------- ------- -------- Net loss attributable to common stockholders.... $(57,848) $(3,010) $(9,307) $(70,165) ======== ======= ======= ======== Basic and diluted earnings (loss) per share: Loss attributable to common stockholders before discontinued operations and extraordinary item... $ (3.54) $ (3.72) Discontinued operations........... (0.02) (0.02) Extraordinary item.... (0.03) (0.03) -------- -------- Total............... $ (3.59) $ (3.77) ======== ======== Weighted-average common shares outstanding-- basic and diluted...... 16,124 2,493(2) 18,617 ======== ======= ======== The accompanying notes are an integral part of this unaudited pro forma consolidated condensed statement. P-3 NOTES TO UNAUDITED PRO FORMA FINANCIAL INFORMATION The unaudited pro forma financial information is based on the following assumptions and adjustments : (1) Reflects the amortization over a three-year life of the excess of purchase price and intangibles of Atcom of $41.9 million over the fair market value of net assets acquired. (2) Reflects common shares issued in connection with the Atcom transaction. P-4