Aetiological factors for enuresis in 68 nightwetting (NW) and 73 day and mixed day and nightwetting (DW/MW) children were examined against a random sample of 142 control children drawn from a population of 3,375 seven-year-old children. Twenty-six variables concerning age, sex, social background, life changes, familial and perinatal history, development, growth, neurological damage, psychic structure and urinary tract disorders were included in the logistic regression analysis. The familial influence on enuresis was clearly seen in both nightwetters and daywetters. The NW children were further discriminated from the controls by items connected with delayed development, such as slower growth and poorer visuomotor and spatial perception. Marital separation or birth of a sibling were also found to be precipitating factors especially for nightwetters. The DW/MW children were discriminated from the controls by perinatal risk factors, signs of neurological dysfunction and smaller voided volume, and especially secondary daywetters by urinary tract infections. These models showed that there are similarities between nocturnal and diurnal enuresis, although there are still many differences and every individual case requires consideration of all these disposing factors.