Purpose: We estimated the spectrum and risk factors for daytime urinary incontinence in school-age children. Materials and Methods: A validated, reproducible, parent administered daytime incontinence questionnaire was distributed to randomly selected school children. The questionnaire elicited information on demographic factors, prenatal and developmental factors, and bowel and urinary history. The spectrum of daytime urinary incontinence was measured by recording the frequency and amount of incontinence. Results: Parents of 2,856 children (mean age 7.3 years) completed the questionnaire. Overall 16.9% reported any daytime urinary incontinence in the previous 6 months, with 64% of cases being very mild, 14.8% mild, 11.6% moderate and 9.6% severe. There was low agreement between frequency and amount of incontinence (weighted kappa 0.03) but risk factors were similar. Independent risk factors were nocturnal enuresis (OR 7.2, 95% CI 3.4 to 15.2), female gender (5.4, 2.6 to 11.1), social concerns (3.4, 1.4 to 8.3), urinary tract infection (5.6, 2.0 to 15.6) and encopresis (3.3, 1.4 to 7.7). Expressed as population attributable risk, 36% of moderate to severe daytime incontinence can be attributed to encopresis, nocturnal enuresis, social concerns, female gender or urinary tract infection. Urinary tract infection was a risk factor for boys but not for girls (interaction p <0.01). Conclusions: Daytime urinary incontinence in children is a common but heterogeneous disorder. Episodes may be frequent or major or both but appear to share the same causal pathway. Given the risk factors identified, interventions should target endogenous/physiological and environmental factors.