Thirty-three patients with advanced carcinoid tumors, islet cell carcinomas, or medullary carcinomas of the thyroid were entered into a phase II trial combining streptozotocin (STZ) and Adriamycin. Thirty-one patients are evaluable for response, and 29 are evaluable for survival. Six (19%) patients achieved objective partial responses (95% confidence limits: 5.4-33). The median duration of response for partial responders was 282 days. The median survival for responders and nonresponders was 16.2 months and 7.8 months, respectively, with an overall median survival of 10.9 months. At 10.9 months median follow-up, 4 (14%) of 29 patients are surviving. Toxicity was mild, except that nausea or vomiting occurred in 25 of 31 patients evaluable for toxicity. With this dose and schedule of administration, STZ and Adriamycin produce modest response rates with objective palliation of disease in patients with advanced amine precursor uptake and decarboxylation (APUD) tumors.