The purpose of this study is to evaluate the antitumor activity of combination carboplatin and etoposide in measurable medulloblastoma. From January '89 to January '92, 26 patients with medulloblastoma were included in a multicentric phase II study of 2 courses of carboplatin 160 mg/m2/d day 1 to day 5 and VP16 100 mg/m2/d day 1 to day 5. Median age was 10 years (19 months-14.5 years). First treatment was surgery alone in 1 patient, surgery + radiotherapy in 4 patients, surgery + chemotherapy in 2 patients less than 3 years old, surgery + radiotherapy + chemotherapy in 19 patients ("8 drugs in 1 day" based:17, SIOP I:1, SIOP II:1). Previous treatment included cisplatin (20 cases), carboplatin (1 case), and VP16 (7 cases). Measurable disease was evaluated by CT scan, MRI or myelogram and CSF. Response rate (RR) was 72 +/- 10%:8 complete responses (CR), 10 partial responses (PR), 1 objective effect (OE), 6 progressive disease (PD), 1 non-evaluable. Thirty-six courses were evaluated for toxicity. Median duration of WHO grade 4 neutropenia was 8 days (0-23). One patient died at day 18 after the first course because of diffuse haemorrhage during septic aplasia. Five other non-life-threatening septicemias were recorded. Median number of platelet transfusions was 1 (0-4). One child who had achieved a PR after two courses died from CNS bleeding after the third course. This drug combination achieves a high response rate in childhood medulloblastoma. Severe toxicity has been mainly encountered in previously heavily treated patients. Tolerance may be acceptable in newly diagnosed children, but careful hematological follow-up and platelet transfusional support are definitely mandatory.