This study examined the school nursing/medical examination records of 6206 national school children for sociodemographic factors associated with reported nocturnal enuresis. A point prevalence of 10.7% (n = 666) for nocturnal enuresis was reported by parents during 1970-1993 in children aged 4-14 years. Although a downward linear trend (from 11.5% to 10.7%) was seen for the reported prevalence of nocturnal enuresis over the 23-year period, this trend was not statistically significant. Age, as expected, large family size and low ordinal position in the family were all statistically associated with reported nocturnal enuresis. Gender was statistically associated with reported nocturnal enuresis only in the 6-14 years age group. Paternal social class was not statistically associated with reported nocturnal enuresis, although 15% of children in families where the father was absent were reported enuretic compared with only 10% of children whose father was in social class 1. These findings contribute to an understanding of the relationship between sociodemographic factors and enuresis as reported at school medical examinations and have implications for the planning and development of health services at local levels.