A phase I/II trial with high-dose etoposide, thiotepa, and dose-adjusted carboplatin (TVCa) with autologous hematopoietic stem cell rescue (AHSCT) as treatment for patients with relapsed or refractory germ cell cancer was investigated. The phase I portion involved a dose escalation schema for carboplatin and thiotepa while keeping the dose of etoposide constant. The intended carboplatin dose was adjusted for renal function based on the glomerular filtration rate. The phase II portion of the trial evaluated the efficacy, feasibility, and safety of tandem TVCa with AHSCT. Twenty-four patients with relapsed or refractory germ cell cancer were treated in this phase I/II trial. Nine of 24 (38%) achieved a complete response. With a median follow up of 71 months (range,1-108 months), all 9 of 24 (38%) are alive and continuously disease-free. There were 2 (7%) treatment-related deaths. The median time to an absolute granulocyte count greater than 0.5 x 10/L was 11 days (range, 9-20 days) on phase I and 10 days (range, 9-13 days) on phase II therapy. The median time to a platelet count greater than 20 x 10/L was 15 days (range, 12-40 days) on phase I and 14 days (range, 13-27 days) on phase II therapy. Nonhematologic toxicity was mild to moderate. A significant correlation was seen between intended carboplatin dose and actual AUC. TVCa high-dose chemotherapy is active and well tolerated in patients with relapsed or refractory germ cell cancer.