Patients are randomized to receive oral 3TC/AZT, ddI/AZT, or ddI alone for at least 24 months. PER AMENDMENT 4/29/96: NOTE: Randomization to ZDV+ddI arm was terminated in Spring of 1996 based upon the results of ACTG 152. Patients on that arm will continue on blinded study drug and will be followed until the end of the study.