There are six study regimens. Four of these are alternating regimens: A 2-week cycle consisting of 1 week of AZT followed by 1 week of ddC and an 8-week cycle consisting of 4 weeks of AZT followed by 4 weeks of ddC. All patients on alternating regimens will receive AZT alone at the standard dose orally every 4 hours for either 1 or 4 weeks. After the AZT is stopped, patients receive ddC orally every 4 hours for either 1 or 4 weeks, which completes a treatment cycle. One of two doses of ddC is studied in each alternating regimen. Both doses must be tested because the optimal dose cannot be inferred from tests that have already been done. AZT is administered first in the hope that AZT-mediated reduction of p24 antigen load may reduce the occurrence of acute ddC toxicity. Two intermittent regimens are also studied and are included to assess the contribution of each drug in the alternating regimens. One program consists of 1 week of AZT followed by 1 week of no drug. The other consists of 1 week of ddC followed by 1 week of no drug. Drug dosing continues for a total of 48 weeks unless toxicity develops. Patients who complete 48 weeks of therapy are followed for 4 additional weeks off therapy. Patients removed from study because of toxicity are followed for 4 weeks or until toxicity resolves. If study participants complete 48 weeks of therapy and meet criteria for efficacy, the study drug regimen may be continued for an additional 32 weeks. A 4 week wash-out period off drug will not be required for patients continuing on study. AMENDED 09/24/90 Drug dosing will be discontinued as of 11/30/90.