A 30-year-old man was admitted with a chief complaint of left-sided scrotal enlargement, and was diagnosed as having testicular seminoma after orchiectomy. Eight years earlier, he had been treated with chemotherapy for an extragonadal germ cell tumor, without orchiectomy, leading to complete remission. His histological diagnosis at that time was a germ cell tumor, composed of choriocarcinoma and embryonal carcinoma. He was followed up without testicular biopsy. Routine pretreatment testicular biopsy in patients with extragonadal germ cell tumor is controversial, but regular long-term follow up and information on the risk of developing a metachronous testicular tumor are needed after treatment of extragonadal germ cell tumors, even when there seems to be a partial or complete clinical response.