Detrusor overactivity is the most common cause of overactive bladder (OAB) and refers to demonstrable involuntary detrusor contractions during urodynamic studies. The number of adults age 40 years or older suffering from idiopathic urge incontinence ranges from 13% in men to 30% in women. For patients whose symptoms are refractory to conventional therapy, intradetrusor botulinum toxin injection offers a safe and effective outpatient treatment with high rates of improvement of OAB symptoms.