Patients are randomized to receive either AZT/ddC, AZT/ddI, AZT alternating monthly with ddI, or AZT/ddI/nevirapine. Patients are evaluated at week 0 and every 4 weeks thereafter for 2 years. Pharmacologic, virologic, and macroneurologic substudies will be conducted. Patients who are already enrolled on protocol ACTG 193 will be given the option of continuing on their originally assigned ACTG 193 therapy for an additional 6 months or undergoing re-randomization to one of the four treatment arms on ACTG 193A.