Histologically pure seminoma with elevated alpha-fetoprotein (AFP), so-called AFP-positive seminoma, is rare. It is recommended that patients with AFP-positive seminoma be managed as non-seminoma, but the clinical features and prognosis of this disease are not fully understood. In this study, we retrospectively analyzed 6 cases of metastatic AFP-positive seminoma at Tsukuba University Hospital (TUH). AFP was elevated before induction chemotherapy in 4 patients with an average of 1,372 ng/ml. In the remaining 2 patients, AFP became elevated during or after induction chemotherapy. In all 4 patients examined, AFPL3% was abnormally increased. As induction chemotherapy, all patients received bleomycin, etoposide and cisplatin (BEP), which was then followed by etoposide, ifosfamide and cisplatin (VIP) in 3 patients. After or during induction chemotherapy, 3 patients suffered from disease progression accompanied by AFP elevation. All 3 were treated by salvage chemotherapy and surgery. Four patients underwent retroperitoneal lymph node dissection (RPLND) after induction chemotherapy ; the pathological findings were necrosis in 3 patients, and viable nonseminomatous cancer in 1 patient. Furthermore, RPLND was performed as salvage surgery in 3 patients ; the pathological findings were necrosis, viable nonseminomatous cancer and teratoma with malignant transformation, respectively. The 5-year progression-free survival rate of the 6 patients was 50%, which is somewhat inferior to that of poor-prognosis non-seminoma patients treated at TUH. One patient ultimately died of cancer, and the remaining 5 are in remission with a median follow-up of 58 months. The present study demonstrates that AFP-positive seminoma patients have a higher risk of relapse compared to non-seminoma patients.