PURPOSE: We determined the effect of 150 units of botulinum-A toxin (Botox, Allergan, Irvine, California) on subjects with severe urge urinary incontinence (UUI). MATERIALS AND METHODS: This was an open label uncontrolled clinical trial. Subjects were recruited from the female urology and urogynecology clinics at Duke University. Inclusion criteria included evidence of UUI on 3-day bladder diary, a 24-hour pad weight of 100 gm or greater, absent or minimal stress leakage, absent detrusor dysfunction, and a history of failed anticholinergic and physical therapies. Exclusion criteria included evidence of a urinary tract infection, or other correctable or neurological etiology for UUI. The detrusor of each subject was injected with 150 units of botulinum-A toxin. Evaluations were performed at 2 weeks, 6 weeks, 3 months and 6 months after injection. Outcome measures included daily incontinence episodes, Urogenital Distress Inventory and the Incontinence Impact Questionnaire, 24-hour pad weights, daily pad usage and urinalysis at all visits. Urodynamic studies were performed at the 6-week and 3-month visits. RESULTS: Three subjects had uncomplicated urinary tract infections during followup. No other adverse effects occurred. Statistically and clinically significant decreases greater than 50% were seen in virtually all outcome measures at all visits up to 3 months. Most subjects showed signs of recurrent UUI by 6 months. All subjects reported remarkable subjective improvement in incontinence. No significant changes in maximal cystometric capacity, maximal detrusor pressure, peak flow or post-void residual volumes were seen. CONCLUSIONS: Botulinum-A toxin can significantly decrease urge urinary incontinence and improve quality of life for 3 months after injection. Additional studies are needed to determine ideal doses, dosing intervals, safety and cost-effectiveness of this therapy.