Although familial PNE probably arises from polygenic inheritance, analysis of a large number of families may enable the identification of major susceptibility loci. Recently, linkage analysis with polymorphic markers identified a locus predisposing to PNE, assigned ENUR1, in a proportion of Danish families.'4The gene resides in a 4 cM interval flanked by markers D13S263 and D13S291 on chromosome 13q.In a clinical and genetic study we examined two aspects of PNE. First, we investigated the genetic predisposition to PNE in 392 cases by recording family history of enuresis. Second, we performed linkage analysis in 16 families segregating for dominant PNE. Materials and methods PATIENTSIn a continuing Swedish multicentre study," 392 children (291 boys and 101 girls) older than 6 years were identified. All showed a severe form of PNE including .10 wet nights out of 28 and absence of a dry period >3 months. Concomitant neurological or urological dysfunction associated with PNE was excluded. Evaluation of each patient included physical examination and urine analysis.A detailed family history was recorded in each case in order to determine the presence of familial PNE as defined by any close relative with PNE beyond the age of 6 years. The parents of affected probands underwent a structured interview with specific questions regarding the onset, frequency, and cessation of bedwetting. Direct contact was made with the relatives when the information from the parents indicated a positive family history for PNE. The diagnosis among second and third degree relatives was ascertained, or excluded, with the same criteria as for the proband. Fam-ily members under the age of 7 years were not included.