PURPOSE Small-cell carcinoma is very aggressive, metastasizes early and often, and does not respond to most chemotherapy regimens. In approximately 50% of cases of prostate cancer, tumors are a combination of small-cell carcinoma and androgen-sensitive adenocarcinoma. It is widely believed that no successful treatment exists for androgen-independent prostate cancer. METHODS A 67-year-old man had undergone androgen ablation therapy and radical prostatectomy for prostate cancer followed by bilateral orchiectomy, limited radiation therapy, and unsuccessful chemotherapy for pain-causing metastatic bone disease. Biopsy and immunohistochemical analysis revealed neuroendocrine differentiation of the cancer. The full extent of metastatic disease was assessed successfully using In-111, a somatostatin derivative. Octreotide acetate was used to treat the tumors. RESULTS In-111 OctreoScan scintigraphy was more sensitive in the diagnostic demonstration of metastatic foci than was bone scanning. Therapy with the cold somatostatin derivative resulted in a rapid and significant relief of pain with significant tumor shrinkage. The patient remained in remission for at least 10 weeks, when he was lost to follow-up. CONCLUSIONS Somatostatin analogs and their radionuclide and cytotoxic derivatives are recommended as adjuvant treatments for prostate carcinoma, especially in those patients who are at high risk for carcinoma recurrence after radical prostatectomy and who have advanced prostate carcinoma at the time of relapse. Because small-cell carcinomas of the prostate and lung are identical, these analogs may be useful in the detection and treatment of these tumors as well.