An intensive study of enuresis nocturna was made on 245 children selected through stratified sampling from a population of 8,462 children. Subjects were 3-15 years and living in a suburban part of Khartoum, Sudan. The prevalence of enuresis nocturna had been found to be high up to the age of ten in the previous extensive study. Few somatic, developmental or behavioural factors, and no family socio-economic or emotional states or child rearing methods including bladder-training, co-varied with enuresis. Climatic conditions and their interaction with possible developmental lags are discussed.