Purpose: We describe the response to conventional or high-dose salvage chemotherapy in patients with advanced seminoma who experience disease progression after receiving first-line platinum-based treatment. Patients and Methods: Twenty-seven patients with progressive, advanced, pure seminoma were treated with salvage chemotherapy. Fifteen patients were treated with conventional-dose cisplatin-and-ifosfamide combination chemotherapy. Twelve patients were treated with high-dose chemotherapy followed by autologous stem-cell rescue. Results: Fifteen patients (56%) achieved a complete response (CR), nine achieved CR with a conventional-dose cisplatin and ifosfamide program, and six experienced CR after high-dose chemotherapy. Fourteen patients (52%) are alive and disease-free, with 13 (48%) continuously disease-free at a median follow-up of 72 months. Twelve (57%) of 21 patients whose pretreatment tumors were studied morphologically were found to have seminoma with atypia. Eight patients underwent resection after salvage chemotherapy; six with histologic findings of necrotic debris/fibrosis alone are alive and disease-free at last follow-up. Both patients with viable seminoma found at surgery died of disease. Conclusion: Most patients with advanced seminoma are cured with standard first-line programs of cisplatin and etoposide with or without bleomycin. A small minority of patients with pure seminoma have resistant tumors and require salvage chemotherapy. In this setting, approximately 50% of patients with recurrent pure seminoma achieve durable CR with conventional or high-dose salvage chemotherapy. Identification of biologic markers to predict clinical outcome and an enhanced understanding of the basic biologic features of seminoma may lead to improvements in the management of this disease.