The aim was to assess the activity of cisplatin (CDDP) in Ewing sarcoma (ES). The study consisted of front-line window therapy with CDDP 120 mg/sqm every 3 weeks for two courses in children and young adults with primary disseminated ES. Response was assessed using the Response Evaluation Criteria in Solid Tumours criteria, and Simon's two-stage design was applied. Twelve consecutive patients were enrolled in stage 1. Only one objective response was observed. Since the target response rate was not achieved, accrual was stopped and CDDP as a single agent in ES was judged unworthy of further assessment.