Twenty-four incontinent elderly institutionalized subjects with detrusor instability participated in a double-blind placebo-controlled trial of oxybutynin chloride. Patients were randomly assigned to oral oxybutynin 5 mg or placebo twice daily. Administration continued for 8 days; a 6-day washout period was followed by the alternative treatment. Incontinence was recorded using a bedside electronic monitor. Four subjects withdrew because of side-effects before completing the trial. There were no clinically significant differences between the oxybutynin and placebo treatments. Both groups experienced side-effects, of which dry mouth was the commonest. Thus, oxybutynin does not appear to be more effective than placebo for the treatment of incontinence in the presence of detrusor instability in elderly institutionalized people.