ADTRAN, Inc. Announces Revised Fourth Quarter Revenue and Earnings Estimate.

HUNTSVILLE, Ala. -- ADTRAN, Inc. (NASDAQ: ADTN) announced revised revenue and earnings estimates for the fourth quarter ending December 31, 2006. Based upon information currently available, revenue for the quarter is expected to range from $108 million to $112 million. GAAP earnings per share for the quarter, assuming dilution, are expected to range from $0.22 to $0.24. Non-GAAP earnings per share for the fourth quarter of 2006, assuming dilution, are expected to range from $0.24 to $0.26. Non-GAAP earnings per share for the fourth quarter of 2006 exclude the effect of stock compensation expense resulting from the application of Statement of Financial Accounting Standards No. 123R, Share-Based Payment ("SFAS 123R"). SFAS 123R was adopted on a modified prospective basis effective January 1, 2006. See the table below for the reconciliation between non-GAAP and GAAP and earnings per share. The revised earnings estimates reflect the anticipated tax benefit from the Tax Relief and Health Care Act of 2006 signed into law on December 20, 2006.

ADTRAN Chief Executive Officer Tom Stanton stated, "This quarter we are experiencing unanticipated softness in order flow, beyond normal seasonality, from some of our larger customers. Our market share and strategic positioning within these customers has never been stronger and we expect the softness we are encountering to be temporary. Overall, we believe our growth drivers remain in place and our outlook for 2007 is strong."

The Company also confirmed that its fourth quarter conference call will be held Tuesday, January 23rd at 9:30 a.m. Central Time. This conference call will be web cast live through StreetEvents.com. To listen, simply visit the Investor Relations site at http://www.adtran.com or http://streetevents.com approximately 10 minutes prior to the start of the call and click on the conference call link provided.

An online replay of the conference call will be available for seven days at http://streetevents.com. In addition, an online replay of the conference call, as well as the text of the Company's earnings release, will be available on the Investor Relations site at http://www.adtran.com for at least 12 months following the call.

ADTRAN, Inc. is one of the world's most successful network access equipment suppliers, with an 18-year history of profitability and a portfolio of more than 1,400 solutions for use in the last mile of today's telecommunications networks. Widely deployed by carriers and enterprises alike, ADTRAN solutions enable voice, data, video, and Internet communications across copper, fiber, and wireless network infrastructures. ADTRAN solutions are currently in use by every major U.S. service provider and many global ones, as well as by thousands of public, private and governmental organizations worldwide.

For more information, contact the company at 800 9ADTRAN (800 923-8726) or via email at [e-mail]. On the Web, visit www.adtran.com.

This press release contains forward-looking statements which reflect management's best judgment based on factors currently known. However, these statements involve risks and uncertainties, including the successful development and market acceptance of new products, the degree of competition in the market for such products, the product and channel mix, component costs, manufacturing efficiencies, and other risks detailed in our annual report on Form 10-K for the year ended December 31, 2005. These risks and uncertainties could cause actual results to differ materially from those in the forward-looking statements included in this press release.

This release includes non-GAAP earnings per share data, which excludes the effect of stock compensation expense for employee stock options associated with the application of SFAS 123R, which ADTRAN adopted effective January 1, 2006. This measure is not in accordance with, or an alternative for, generally accepted accounting principles and may be different from non-GAAP measures used by other companies. ADTRAN believes that the presentation of the non-GAAP measure, when shown in conjunction with the corresponding GAAP measure, provides useful information to management and investors regarding financial and business trends relating to its financial condition and results of operations. In particular, as ADTRAN applies SFAS 123R, it believes that it is useful to investors to understand how the expenses associated with the application of SFAS 123R are reflected in its results of operations. The presentation of the non-GAAP measure permits both investors and management to more readily compare past results, which do not include the impact of SFAS 123R, with future results, and to better understand ADTRAN's performance over the periods presented.

[TABLE OMITTED]