The proportion of patients with metastatic germ cell tumors achieving complete remission increased, and the total survival improved between 1975 and 1982. Several analyses were undertaken to evaluate the influence of stage migration on treatment outcome in patients with germ cell tumors. (a) A logistic regression analysis showed that a formulation of time was an independent statistically significant variable (P = 0.025) in addition to the total number of sites of metastasis (P less than 0.001) and pretreatment values of human chorionic gonadotropin (P less than 0.001) and lactate dehydrogenase (P = 0.002). (b) The proportion of patients with lung metastases and elevated levels of human chorionic gonadotropin and alpha-fetoprotein decreased, and the number of patients with retroperitoneal metastases and without prior radiation therapy increased significantly. (c) The number of patients with a high likelihood of complete response increased significantly over time (P less than 0.001). Computerized tomography of the abdomen permits detection of large but asymptomatic retroperitoneal disease, and such patients are now being treated with chemotherapy rather than surgery and are included in advanced disease treatment results. Stage migration has played a role in the increasing proportion of complete responders in clinical trials of patients with germ cell tumors.