Patients with brain metastases from small cell lung cancer (SCLC) have a poor prognosis. Although most patients die from metastatic disease outside the central nervous system, this disabling metastatic site often needs treatment to mitigate the signs and symptoms of intracranial disease. The effect of carboplatin (400 mg/m2 every 4 weeks) as second line treatment for recurrent or progressive brain metastases was studied in 20 SCLC patients. 19 patients could be evaluated: 16 by contrast enhanced brain computer tomography (CT) scan (2 patients had complete response, 6 partial response, 4 stable disease and 4 progressive disease) and 3 patients clinically, who had progressive disease. The objective response rate in the brain was 40% (95% CI:22-61%). The median response duration was 8 weeks (range 2-29). The median survival was 15 weeks (range 1-44). Previous cranial irradiation appeared to be beneficial for survival. There was only mild haematological and gastrointestinal toxicity. Carboplatin has activity against brain metastases and gives palliation in responding patients.