Acute tumor lysis syndrome (ATLS) is a well-known adverse event described after effective chemotherapy for extensive, highly proliferative, and chemosensitive tumors. While its occurrence with hematological malignancies is frequently described, there have been scattered case reports documenting ATLS in solid tumors. However, such events have not been reported in poor-risk germ cell tumors. We reviewed retrospectively 46 cases of such tumors treated in our department between 1988 and 1993 by aggressive cisplatin-based chemotherapy. All patients received systematically 6 l/24 h hydration according to the cisplatin- protocol administration. Blood chemistry data for potassium, phosphorus, calcium, alkaline reserve, uric acid, creatinine and lactate dehydrogenase were obtained before treatment and during the 7 days of the induction chemotherapy. No metabolic abnormalities suggestive of ATLS were observed. Nevertheless, 2 patients with bulky disease of the chest experienced early death from respiratory distress complicated by multiorgan failure. ATLS seems to be an unlikely event in poor-risk germ cell tumors and therefore special prophylactic therapy may be unnecessary.