From 1978 to 1984, 62 patients with advanced seminoma of testicular or extragonadal origin were entered on two consecutive Southeastern Cancer Study Group (SECSG) protocols. All patients had progressive disease and were stratified according to tumor burden. Randomization on SEG 78-GU240 was cisplatin, vinblastine, and bleomycin (PVB), with or without doxorubicin; on SEG 81-GU332, randomization was to PVB or cisplatin, etoposide (VP-16), and bleomycin (PVP16B). Dosages of etoposide, vinblastine, and doxorubicin were decreased by 25% in patients who had received prior radiotherapy. Thirty patients (55%) had received prior chest and/or abdominal radiotherapy. Overall, 41 of 60 evaluable patients (68%) achieved a complete remission (CR) and 37 patients are alive and free of disease. CR was obtained in 13 of 15 patients (87%) with minimal disease, 13 of 16 (81%) with moderate disease, and 15 of 29 (52%) with advanced disease. Patients with no prior radiotherapy or limited-field (chest or abdomen) radiotherapy were more likely to achieve CR than those with prior chest and abdominal radiotherapy (75% v. 42%). Using univariate analysis, the extent of disease is the only significant prognostic factor, whereas both extent of disease and extent of prior radiotherapy are significant in a multivariate analysis. This study confirms the chemosensitivity of metastatic seminoma in a cooperative group setting and defines prognostic factors useful for comparison of other chemotherapeutic trials in seminoma.