Eighty-seven patients with primary mediastinal germ cell tumors treated between 1983 and 1990 were studied. Among the 23 patients classified as pure seminoma, eight (35 percent) underwent surgery followed by radiotherapy (n = 6), radiotherapy and/or chemotherapy (n = 2); two patients underwent radiotherapy; 13 patients (57 percent) underwent induction cisplatin-based chemotherapy (ten complete responses) followed by radiotherapy (n = 9), second line chemotherapy (n = 2) and surgical resection of residual tumor (n = 2). On completion of treatment, 22 patients (96 percent) with seminoma were free of disease. The two-year Kaplan-Meier survival rate of these patients was 86 percent. Among the 64 patients with nonseminomatous germ cell tumor, 19 patients (30 percent) underwent surgery as first treatment (ten complete resections) followed by chemotherapy (n = 17) and radiotherapy (n = 5). On completion of treatment, 12 of 19 patients were disease free. Forty-five patients (70 percent) underwent induction cisplatin-based chemotherapy (ten complete responses), and 22 of them underwent resection of residual tumor (19 complete resections). Twenty-three patients were treated with first line chemotherapy without postchemotherapy surgery (three complete responses). In summary, 33 patients (52 percent) with nonseminomatous germ cell tumors became free of disease, and seven patients (21 percent) relapsed after achieving a complete response. The two-year Kaplan-Meier survival rate of the nonseminomatous germ cell tumor patients was 53 percent (87 percent if a complete response), with a median survival of 28 months. Despite a worse prognosis than nonseminomaous tumors from other primary sites, this series of mediastinal germ cell tumors has confirmed the efficacy of therapy.