The prognostic significance of certain factors in the outcome of the haemolytic-uraemic syndrome (HUS) was evaluated. Seventy-three children with HUS were observed; 35 recovered without residual abnormalities, 6 had normal renal function with hypertension (HT) and/or urinary abnormalities, 5 had chronic renal failure, 1 child required chronic dialysis treatment, 4 children died of end-stage renal failure, and 22 died of acute renal failure (ARF). To identify the risk factors which influence prognosis, a logistic discrimination method was used to analyse the clinical and laboratory data. The logistic discrimination method established the role of independent factors which were linked together. The grouping of the patients in three different categories of favourable and unfavourable prognosis yielded conclusions concerning: (1) outcome of ARF survivors (2) recovery without sequelae or all other outcomes including death; (3) survival or death. The most important unfavourable factors for recovery of ARF survivors were HT and to a lesser degree cardiovascular (CV) disturbances; for recovery of the entire group, and for survival, the presence of CV disturbances was the worst prognostic factor. Among other factors were seasonal incidence, central nervous system disturbances, prodromal symptoms and age, which varied in their prognostic significance in the various groups.