— A mixed study of prevalence and incidence of enuresis carried out at schools in the province of Sassari was planned over a 2-year period. 734 children aged between 3 and 11 years from 3 schools representative of the urban, suburban and rural areas of Sassari, were selected by “cluster” sampling. In this first stage of the project a study of prevalence on children aged 3, 6 and 9 years was carried out. The second stage encompassed a 2-year longitudinal study on those selected in the first stage and provided incidence data pertinent to children aged 4, 7 and 10 years. At the end of the second year of follow-up incidence data relative to children aged 5, 8 and 11 years will be available. Information about children's families and possible urologic disease was collected by means of a questionnaire. Urologic examination then followed. Cross sectional study. In the 73 children aged 3 years, who attended nursery schools, 7 cases of enuresis (9.6%) were ascertained. In the 306 6-year-old children of the first year of primary school, 22 cases of enuresis (7.2%) were observed. In the 355 9-year-old students of the fourth year of primary school, 10 cases (2.8%) were reported. Focusing on the geographical origin of the students, we observed 11 cases of enuresis (5.2%) in cluster I (suburban quarter), 11 cases (6.3%) in cluster II (urban area), and 17 cases (4.9%) in cluster III (rural area). Follow-up. No case of enuresis was observed among the nursery school children (aged 4 years); 2 new cases (0.7%) were ascertained in the 7-year-old group. In the group of children aged 10, only 1 new case (0.57%) was encountered. Taking into account the results of every single cluster, we observed 2 new cases (0.99%) in cluster I, one (0.61%) new case in cluster II and no cases in cluster III. Prevalence of enuresis reached 5.3% in the whole sample, showed a progressive decrease from the younger to the older age group (9.6% in 3-year-olds; 7.2% in 6-year-olds and 2.8% in 9-year-olds), with a clear though not significant male predominance. When data were analysed according to geographical “clusters” a higher prevalence of enuresis was observed among subjects living in the urban area (cluster II). Our results did not differ significantly from those collected by other Authors in similar surveys (Bloom 1993).