To define risk groups in children with acute myeloid leukaemia (AML), we conducted a multivariate stepwise Cox regression analysis of three consecutive multicentre studies in East Germany. The total number of patients was 240, but cytogenetics and remission status on day 15 were routinely investigated only in the most recent study, AML-III/93 (78 patients). We derived an equation to calculate individual risk factors, determined those risk factors for all patients of study AML-III/93 and divided them into three groups with 26 patients in each. The variables in the equation were: WBC, FAB-type, auer rods, cytogenetics and response status on day 15. The event-free survival was 80% in the low risk, 55% in the intermediate risk and 15% in the high risk group. Our results strongly suggest that calculating individual risk factors on the basis of a multivariate stepwise Cox regression analysis is a useful tool in defining risk groups.