Seventy-seven patients with primary malignant testicular tumors were treated in our hospital. Twenty-five of them were given antineoplastic agents containing cis diamine dichloro platinum (CDDP). In three long-term survivors, new malignant testicular tumors developed meta-chronously and had different histological findings from those of the initial tumors. Case 1. A 28-year-old patient with a yolk sac tumor of the left testicle, stage IIO, developed metastasis to the supraclavicular lymph nodes five years after radiation. Chemotherapy containing of VP-16 (837 mg), CDDP (1050 mg), vincristine (32 mg), bleomycin (480 mg), and actinomycin-D (16 mg) achieved complete remission. Four years 11 months later a seminoma of the contralateral testicle, stage I, was disclosed and he died of cancer 11 years and four months after the onset of the initial disease. Case 2. A 30-year-old patient with testicular teratoma, stage IIIA, on the right side gained complete remission after a CDDP containing chemotherapy. One year and four months after the beginning of the CDDP use (1,300 mg totally as CDDP) a seminoma on the contralateral side, stage I, was detected. He died of cancer eight years and two months after his initial tumor was detected. Case 3. A 37-year-old patient with combined tumor of seminoma and yolk sac tumor of the right testicle, stage IIIO, was free from disease for six years and five months under chemotherapy. At this point a seminoma, stage I, of the contralateral testicle was newly found and treated by radiation.(ABSTRACT TRUNCATED AT 250 WORDS)