Thirty patients with anorexia nervosa and 30 controls had an electrocardiogram with the corrected Q-T interval. The aim of the study was to analyse the corrected Q-T interval in patients with anorexia nervosa compared with the findings in the control group, to compare the body mass index between two groups and to measure underlying dispersion of the corrected Q-T interval in each of the 12 ECG leads in both groups. All corrected Q-T intervals were measured in each of the 12 ECG leads and the longest values of three consecutive intervals were used for this analysis. The prolonged corrected Q-T interval was found in 12 out of 30 patients with anorexia nervosa (40%), with the longest mean values of 0.421 s (range, 0.334-0.500 s), and in 2 out of 30 patients of the controls (7%), with the longest mean values of 0.390 s (range, 0.343-0.444 s). The difference was statistically significant (t = 4.453, P < 0.001). Relative risk for prolongation of the corrected Q-T interval in patients with anorexia nervosa was high: 12 compared with control subjects. The longest values of the corrected Q-T interval in both groups, and the longest values of the prolonged corrected Q-T interval in both groups were observed in the anteroseptal leads of the electrocardiograms. The mean serum potassium level in the group with anorexia nervosa was 3.97 and in the control group was 4.15 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)