The aim of the present study was to investigate the aggregation of cardiovascular risk factors (hyperinsulinaemia, impaired glucose tolerance, dyslipidaemia, and hypertension) in 180 (77 female, 103 male) obese and 239 control children. Blood glucose, serum insulin and lipid levels were determined from blood samples taken after an overnight fast. Oral glucose tolerance tests were performed and blood glucose concentrations were monitored. The body mass index, body fat (on the basis of skinfold measurements), lean body mass and waist/hip ratio were calculated and blood pressure was measured five times in all subjects. It was shown that only 14.4% of obese children were free from any risk factors, in contrast to 79.1% of the control children. Four risk factors (metabolic cardiovascular syndrome) were found in 8.9% of the obese children (8.7% in males and 9.l % in females) while none could be detected in controls. Considerable differences were also detected in the prevalence of one, two or three risk factors between control and obese children. Patients with the metabolic cardiovascular syndrome could not be characterized by any of the investigated anthropometric characteristics, but the duration of obesity was significantly longer in these children.