Exhibit 21 Exhibit 21 - Subsidiary List List of Subsidiaries of AT&T Corp. As of 3/28/02 Jurisdiction of Incorporation ACC Corp................................................. Delaware Alascom, Inc............................................. Alaska AT&T Communications, Inc................................. Delaware AT&T Communications of California, Inc................... California AT&T Communications of Delaware, LLC..................... Delaware AT&T Communications of Hawaii, Inc....................... Hawaii AT&T Communications of Illinois, Inc..................... Illinois AT&T Communications of Indiana, Inc...................... Indiana AT&T Communications of Maryland, LLC..................... Delaware AT&T Communications of Michigan, Inc..................... Michigan AT&T Communications of the Midwest, Inc.................. Iowa AT&T Communications of the Mountain States, Inc.......... Colorado AT&T Communications of Nevada, Inc....................... Nevada AT&T Communications of New England, Inc.................. New York AT&T Communications of New Hampshire, Inc................ New Hampshire AT&T Communications New Jersey Holdings, LLC............. Delaware AT&T Communications of New York, Inc..................... New York AT&T Communications of Ohio, Inc......................... Ohio AT&T Communications of the Pacific Northwest, Inc........ Washington AT&T Communications of Pennsylvania, Inc................. Pennsylvania AT&T Communications of the South Central States, LLC..... Delaware AT&T Communications of the Southern States, LLC.......... Delaware AT&T Communications of the Southwest, Inc................ Delaware AT&T Communications of Virginia, LLC..................... Virginia AT&T Communications of Washington D.C., LLC.............. Delaware AT&T Communications of West Virginia, Inc................ West Virginia AT&T Communications Holdings of Wisconsin, LLC........... Delaware AT&T Communications Services International Inc........... Delaware AT&T Global Communications Services Inc.................. Delaware AT&T Solutions Inc....................................... Delaware AT&T Global Network Services Inc......................... Delaware AT&T of Puerto Rico, Inc................................. New York Teleport Communications Group Inc........................ Delaware AT&T Broadband LLC ...................................... Delaware MediaOne Group, Inc. .................................... Delaware