We describe the use of amrubicin hydrochloride to treat small cell carcinoma of the prostate in a 23-year-old man. Initial radiological examinations of the patient revealed a pelvic tumor associated with bilateral hydronephrosis, pelvic lymph node swelling, and lumbar vertebral bone metastases. The pathological diagnosis was small cell carcinoma originating in the prostate, based on positive immunohistochemical staining for neuron-specific enolase, synaptophysin, and myoglobulin; and negative staining for CD3e, CD20, leukocyte common antigen, and CD99. The clinical stage was T4N1M1. A bilateral nephrostomy was performed to improve renal function, and an ileostomy was established to prevent ileus. The first induction chemotherapy consisted of amrubicin 35 mg/m(2) (days 1, 2, 3, monthly). The amrubicin regimen caused a dramatic reduction in tumor size, but could not be continued, because of the occurrence of grade 4 diarrhea. A different regimen was then administered, consisting of one cycle of a 50% dose and a second cycle of a 75% dose of etoposide (100 mg/m(2) days 1, 2, 3), coadministered with carboplatin (AUC 5, plasma concentration curve). Five months after the induction of chemotherapy, the patient suffered respiratory arrest and died.