In Phase I, eligible patients with advanced Kaposi's sarcoma are randomly assigned to either ddI or ddC in combination with DBV chemotherapy. On the average, patients receive 12-44 weeks of combined chemotherapy and antiretroviral therapy. If vincristine is deleted from Phase I because of excess neurotoxicity, it will not be administered as part of the combination chemotherapy if that treatment is continued in the Phase II study. The Phase II trial proceeds when at least six cycles (12 weeks) of DBV have been completed by six patients enrolled in Phase I, and an overall evaluation of tolerance to each combination treatment plan has been completed. Study medication is administered as in Phase I, with the possible deletion of vincristine. All patients who complete DBV chemotherapy with complete or partial response or stable disease will continue to receive the originally assigned investigational antiretroviral drug (ddC or ddI) for an additional 24 weeks.