To evaluate the safety and efficacy of low and high doses of lamivudine ( 3TC ) in combination with zidovudine ( AZT ) and zalcitabine ( dideoxycytidine; ddC ) in combination with AZT.

PER 02/27/95 AMENDMENT: To evaluate the efficacy and safety of both blinded and open-label combination therapy.

Patients are randomized to one of three treatment arms: low-dose 3TC plus AZT, high-dose 3TC plus AZT, or ddC plus AZT. Treatment continues for 32 weeks, with possible extension to 52 weeks.

PER 02/27/95 AMENDMENT: Patients may continue therapy on AZT and low-dose 3TC on an open-label basis. Open-label therapy continues with follow-up every 8 weeks until intolerable toxicity occurs or study terminates.

Inclusion Criteria

Patients must have:

• HIV positivity.
• CD4 count 100-300 cells/mm3.
• Prior AZT therapy for 24 or more weeks and currently on AZT.

Exclusion Criteria

Patients with the following prior conditions are excluded:

• History of intolerance to AZT.
• History of grade 2 or worse peripheral neuropathy.

Prior Medication:

Excluded:

• Any prior antiretroviral therapy other than AZT.

Required:

• Concomitant AZT therapy.

Required:

• At least 24 weeks of prior AZT.