Thirty-five cases of incontinence of urine due to hyperactivity of the detrusor as a result of unstable urinary bladder were found among 100 patients with incontinence. The cause of the hyperactivity was established after a thorough urological and neurological screening with intravenous urography, seriated mictional cystoureterography, cystoscopy, and urine culture. The diagnosis was considered definite if uninhibited contractions of the detrusor were detected by electrocystomanometry. The primary clinical symptom was an imperious urge to mi-turate, with or without leakage of urine. Diurnal and nocturnal frequency was exacerbated in cold weather and in contact with water. There were some instances of a history of late enuresis and association with cystoceles. Anticholinergics (propantheline bromide) are the treatment of choice. Surgery should be indicated only after all medical attempts have failed.