In order to evaluate differences in sleep factors between children with wetting problems and dry children, questionnaire data were obtained from 1,413 schoolchildren between the ages of 6 and 10 y. The analyses were performed using logistic regression, and adjusted odds ratios (ORs) were calculated to approximate the relative risk. Current enuresis was associated with a subjectively high arousal threshold, pavor nocturnus, nocturia and confusion when awoken from sleep (ORs 2.7, 2.4, 2.1 and 3.4, respectively), whereas children with current incontinence often experienced bedtime fears, onset insomnia or nocturia (ORs 2.4, 2.3 and 2.7, respectively). Children exhibiting urinary urgency were overrepresented among both children with current enuresis (OR 2.5) and those with current incontinence (OR 17.2). It is concluded that impaired arousal mechanisms and bladder instability are aetiological factors underlying nocturnal enuresis.