Primary bed-wetting poses serious problems to children who suffer it and to their families. Based on studies that showed a circadian cycle of ADH, a new treatment of primary enuresis using DDAVP (1 desamino-8-D-arginine-vasopressin) has been proposed. The purposes of this study were: a) to monitor night time endogeneous ADH secretion in 10 patients with non-complicated primary enuresis. b) To evaluate a randomized treatment with oral DDAVP or placebo in 30 patients with primary non-complicated enuresis. MATERIAL AND METHODS: a) monitoring ADH secretion was carried out in 6 nocturnal blood samples, between 10 PM and 5 AM. ADH was measured by radoinmunossay; b) response to treatment was evaluated on a weekly basis, for 4 weeks. When there was lack of response after 2 weeks the initial dose of 0.2 mg was doubled. RESULTS: a) endogenous ADH dosages did not show significant variations throughout the nigth. In no case we observed high values; b) Of the 23 patients evaluated (12 with DDAVP and 11 with placebo), a positive response (≥ 65% reduction of weekly enuretic episodes) was observed in 50% DDAVP treated patients and in 23% of placebo ones.CONCLUSIONS: The ADH dosages showed lack of the increased nocturnal secretion described in normal persons. This could endose the use of DDAVP in enuretic children. The response to treatment showed a significant difference in favor of DDAVP compared to placebo treatment (P<0.05). No side effects were observed in patients treated with DDAVP.