Urine production is reduced at night allowing undisturbed sleep. This study was undertaken in order to show the effect of sleep deprivation (SD) on urine production in healthy children. Special focus was on gender and children at an age where enuresis is still prominent. Twenty healthy children(10 girls) underwent two 24-hour studies, randomly assigned to either sleep or sleep deprivation. Diet and fluid intake were standardized. Blood samples were drawn every fourth hour during daytime and every two hours at night. Urine was fractionally collected. Blood pressure and heart rate were non-invasively monitored. Blood was analyzed for plasma antidiuretic hormone(AVP), atrial natriuretic peptide(ANP), angiotensinII, aldosterone, and renin. Urine was analyzed for aquaporin2 and prostaglandinE2. Successful sleep deprivation was achieved in all participants with a minimum of 4h 50min and full-night sleep deprivation was obtained in 50% of the participants. During sleep deprivation both boys and girls produced markedly larger amounts of urine than during normal sleep(477±145 vs. 291±86 ml, p