To assess the prevalence and characteristics of enuresis nocturna in adults, the treatment they received and the perceived impact, a random sample of 13081 non-institutionalized adults (18-64 years old) were asked to participate in the study in January-March 1996. The response rate was 87%. A personal computer questionnaire included 23 questions on frequency of bedwetting, daytime wetting, treatment and perceived impact. Any respondent reporting bedwetting at least once during the previous 4 weeks was considered to have enuresis nocturna. The overall prevalence of enuresis nocturna was 0.5%. Differences between age groups and sexes were not significant. Fifty percent of men and 19% of women reporting enuresis nocturna had primary enuresis nocturna, of those with enuresis nocturna, 12% of men and 29% of women had always daytime incontinence. Fifty percent of the men and 35% of the women had never consulted a care provider for their bedwetting and 38% of the men and 26% of the women had done nothing to become dry. Only 30% believed that bedwetting was treatable. Bedwetting was associated with several psychosocial problems. Enuresis nocturna in adults is common and may lead to embarrassment and discomfort. It may affect careers, social life and personal relationships. Adults should be more aware that bedwetting is a treatable problem. More information should be given on this issue.