Enuresis is a common functional problem among children which is defined as a complete involuntary voiding of urine at an age which control should be present. Bed wetting generally resolves with increasing age, but the restriction in social life and the psychological secondary problems, so frequent in older patients, justify an appropriate treatment of the problem in the child over seven. At children's Hospital of Florence University an enuresis service exists since 1983, and during these years 541 children applied to the structure. 326 children completed the treatment, among these there were 202 boy and 124 girls with age between 6 and 19. All the patients have been initially helped only with conversation (motivational counseling) and 76 among them (23% of the whole) obtained permanent cure. The remaining 250 children were treated with the conditioning alarm system, always associated to periodic conversation, urine stop exercises and other psychological support (token economy, etc). There were 161 boys and 89 girls: 220 children had nocturnal primary enuresis and 30 secondary. The family history was positive in 77%. The results obtained of this kind of treatment after a follow-up of 6 months, were permanent recovery in 211 children (84%) and failure in 39 patients (16% of the cases). There have been 35 relaxes. Regarding the sex, no significant difference was noted. These positive results with the conditioning devices favor the view that the etiology of primary enuresis is mainly biologic. The bell alarm represents the most effective treatment for nocturnal enuresis included more than seven.(ABSTRACT TRUNCATED AT 250 WORDS)