A total 2535 cases of Wilms' tumours registered in children aged 0--14 years by 34 population-based cancer registries in 16 countries of Europe in 1978--1992 and followed-up until the end of 1994 were included in this EUROCARE study. Overall 5-year observed survival of all children diagnosed in 1985--1989 was 83%, 95% confidence interval (CI) 80--85. Relatively large differences were observed between the European countries, with significantly lower survival of patients registered in the formerly socialist countries, Estonia, Poland and Slovakia. Overall European survival was slightly lower in comparison with results reported from the USA and Australia, which demonstrate a potential for improvement. Over the study period, overall survival adjusted for age, sex and country has increased significantly. This favourable trend is attributed primarily to improvements in treatment, particularly to the introduction of new chemotherapeutic agents.