Patients with primary nocturnal enuresis were entered into 4 treatment groups: observation, imipramine, desmopressin acetate or alarm therapy. Patients were weaned from therapy 6 months after inclusion in the study and were evaluated for continence at 3, 6, 9 and 12 months after beginning the study protocol. Of the 50 patients under observation 6% were continent at 6 months and 16% were continent within 12 months. Of 44 patients treated with imipramine 36% were continent at 6 months on medication; however, only 16% were continent at 12 months, off medication. Similarly, of the 88 patients treated with desmopressin acetate 68% were continent at 6 months but only 10% were continent at 12 months. Of the 79 patients treated with alarm therapy 63% were continent at 6 months and 56% were dry at 12 months. Although each form of therapy improved continence over observation alone (p < 0.01), only the bed-wetting alarm system demonstrated persistent effectiveness (p < 0.001).