Twenty nine patients (median age 12 years) with a CNS tumour, received platinum-based chemotherapy for assessable disease. In 23 patients there was an objective response with improvement lasting for a median duration of 11 months. There was little difference in the response to cisplatinum or carboplatin therapy. The response rates in specific disease groups were: medulloblastoma 8/10, two with a complete response (CR) and six with a partial response (PR); ependymoma 1/5 PR; pineal retinoblastoma 5/5 with three CR and two PR; primitive neurectodermal tumours (PNET) 2/2 PR and pineal germ cell tumours 6/6 with four CR and two PR. It is concluded that platinum-based chemotherapy has a beneficial effect on CNS tumours of the CNS, especially medulloblastoma, ectopic intracranial retino-blastoma and pineal germ cell tumours.