Although testicular germ cell tumor is a relatively uncommon disease, it is a relatively common type of malignant tumor among young men. Seminoma accounts for approximately 50% of all germ cell testicular tumors. Since the vast majority of patients with seminoma present with early-stage disease and the disease responds well to treatment, almost all of the patients are cured. Patients who have stage I disease without obvious metastatic lesions have two treatment options, surveillance or adjuvant retroperitoneal radiotherapy, following inguinal orchiectomy. Stage IIA disease with a relatively small retroperitoneal lymph node metastasis is generally treated by retroperitoneal radiation therapy, although systemic chemotherapy with carboplatin is an alternative treatment. For patients with bulky retroperitoneal lymph node or distant metastases (stage IIB, III), systemic chemotherapy including cisplatin and etoposide appears to be the standard approach. Recently, 85% to 90% of patients with stage III disease are cured. Thus, the current therapeutic goal is cure of the disease with the minimum of treatment sequelae.