Groups of 10 patients are studied at each of three dose levels. Five patients at each dose level have less than 3 months of prior AZT treatment; five patients at each dose level have at least 12 months of previous AZT treatment and tolerated an AZT regimen of 600 mg/day (200 mg every 8 hours). At least 24 patient-weeks of treatment with the combination treatment must be completed without requiring dose interruption before the next dosage level can be started. All 30 patients must be enrolled at a lower dosage level before a higher dosage level is started. Patients begin treatment with AZT. 14 days later, patients begin treatment with nevirapine in addition to the AZT. After 24 weeks, patients have the option to continue long-term treatment with either nevirapine or standard treatment.