Patients are randomly assigned to 1 of 3 treatment groups. In study arm 1, patients receive AZT plus ddC placebo. In study arm 2, patients receive ddC plus AZT placebo capsules. In study arm 3, patients receive ddC plus AZT. Patients are seen every other week for first 8 weeks and monthly thereafter. Patients are stratified by HIV disease status, length of time receiving AZT, and systemic or local Pneumocystis carinii pneumonia (PCP) prophylaxis. Patients who reach a clinical AIDS-defining endpoint are offered open-label combination therapy.