OBJECTIVE We prospectively evaluated the efficacy of a combination of desmopressin and oxybutynin for treating children with nocturnal enuresis, compared to the single drugs imipramine and desmopressin. METHODS We enrolled 158 patients from 2003 to 2004. Children were randomly assigned to 1 of 3 groups and treated with desmopressin, imipramine or a combination of desmopressin plus oxybutynin. Of these patients 145 (100 boys and 45 girls, mean age 7.8 +/- 2.5 years, range 5 to 15) were followed for more than 6 months. Efficacy was measured at 1, 3 and 6 months in terms of average enuretic frequency, 5-scale response based on change in nocturnal enuretic frequency after treatment and posttreatment enuretic frequency as a percentage of pretreatment baseline frequency. The latter efficacy was classified according to daytime voiding symptoms. Statistical evaluation was performed using chi-square tests and ANOVA. RESULTS Of the 145 children followed 48 received combination therapy, 49 received desmopressin and 48 received imipramine. A total of 68 patients (47%) had monosymptomatic enuresis and 77 (53%) had polysymptomatic enuresis. Combination therapy produced the best and most rapid results regardless of whether the children had monosymptomatic or polysymptomatic enuresis. CONCLUSIONS Combination therapy with desmopressin plus oxybutynin for the treatment of pediatric nocturnal enuresis was well tolerated, and gave significantly faster and more cost-effective results than single drug therapy using either desmopressin or imipramine.