We investigated the antitumor activity and toxicity of cisplatin and interferon-alpha 2B as the primary treatment of penile carcinoma. A total of 13 consecutive patients with nonmetastatic, histologically confirmed invasive squamous cell carcinoma of the penis underwent treatment consisting of 20 mg./m.2 cisplatin intravenously and 5 x 10(6) mu./m.2 interferon-alpha 2B subcutaneously daily for 5 consecutive days. An equivalent dose of interferon was then administered subcutaneously every 2 days for 3 weeks and the regimen was repeated at 28-day intervals. Of 12 evaluable patients 9 responded: 4 achieved a pathologically confirmed complete remission of 38+, 21+, 10 and 7 months in duration (2 with relapse were treated with local therapy and remain with no evidence of disease), and 5 achieved a partial response, underwent surgical removal of residual disease and remained disease-free for 14+ to 24+ months. The most significant toxicities were anemia in 5 patients and reversible renal impairment in 3 but no patient had neutropenic fever or required platelet transfusion. We conclude that primary treatment with cisplatin and interferon-alpha 2B induced responses in 75% of 12 patients with penile carcinoma and allowed for a less radical operation than originally scheduled. A larger number of patients and longer followup will be required to confirm these encouraging preliminary results.