We treated 63 patients with urinary symptoms associated with uninhibited detrusor contractions on cystometry by prolonged bladder distension. All patients had received drug therapy previously without success. Fourteen patients whose symptoms relapsed after a previous distension or who failed to obtain any improvement have had repeat distension. Postoperative cystometry was done in 36 cases. Only in 7 patients (19 per cent) did the unstable pattern convert to stable bladder function. The results of symptomatic assessment were dependent upon the moment of followup, since many patients had relapses. After a 3-month followup 17 per cent of the patients were cured and 19 per cent noticed some symptomatic improvement. A subjective evaluation after 1 year revealed 11 per cent cured and 21 per cent improved. The results after a second distension were even less than after prior distension. Complications included a ruptured bladder in 6 female subjects (8 per cent), 2 patients were temporarily unable to void spontaneously, while 1 patient still had atony of the bladder after 6 months of followup. Bladder distension appears to be of limited or doubtful value in the treatment of the patient with an unstable bladder. Moreover, when the high incidence of complications is considered we do not recommend this therapy to be pursued further.