The response of desamino-D-arginine vasopressin (DDAVP) was investigated in 32 enuretic children in a double-blind clinical study. The 15 children treated with DDAVP showed a significant reduction in the incidence of bed wetting - from 18.7 ± 6.5 to 6.5 ± 9.2 wet nights per 30 days. In 6 children bed wetting stopped entirely, in 6 there was a satisfactory response, and in 3 the response was marginal or there was none. When DDAVP was stopped most children reverted to their earlier bedwetting habits (15.7 ± 8.9 nights a month). Response to DDAVP was significantly better in children aged more than 10 years (mean age for the entire group). The administration of DDAVP was not associated with any appreciable change in morning urine osmolalities. No adverse effects were noted. It is concluded that DDAVP is effective in nocturnal enuresis, particularly in older children. It is suggested that the cessation of bed wetting may, in part, reflect functional properties of DDAVP rather than antidiuresis.