Patients are randomized to either a ddI limb or d4T limb, then randomized a second time to one of six treatment arms, as follows: ddI alone, d4T alone, 3TC/AZT (on both ddI and d4T limbs), 3TC/ddI, and 3TC/d4T. Treatment is given for 48 weeks. At study week 24, patients on monotherapy will have 3TC added to their regimen (in a blinded fashion).