Inclusion Criteria:

1. Male between 40 and 90 years of age.
2. Clinical signs and symptoms of frequency and urgency
3. Urodynamic history consistent with OAB that developed in conjunction with Benign Prostate Obstruction and that persists for at least 3 months post TURP or PVP, or other obstruction relieving procedure.
4. OAB inadequately controlled with anticholinergic medications
5. Qmax >12mL/s with a voided volume of >125mL.
6. IPSS >12, with IPSS QoL >3 at study Visit 1.
7. Willing to use clean intermittent catheterization (CIC) to empty the bladder or is willing to have an indwelling catheter, if necessary following study treatment.

Exclusion Criteria:

1. Known history of interstitial cystitis, uninvestigated hematuria, bladder outlet obstruction due to vesical neck contracture, mullerian duct cysts, urethral obstruction due to stricture/valves/sclerosis of urethral tumor, radiation cystitis, genitourinary tuberculosis, bladder calculi, or detrusor-sphincter dyssynergia.
2. Current indwelling catheter, or removal of chronic catheter <1 month prior to study entry.
3. Non-compliance with wash-out periods for prohibited medications/therapies
4. Evidence of Urinary Tract Infection according to local standard of care.
5. History of prostate cancer.
6. Serum PSA of >10ng/mL. [NOTE: Subjects with serum PSA concentrations >4 and <10 must have prostate cancer excluded according to the local standard of care.]
7. 24 hour total volume voided >3000 mL of urine
8. Medical condition that may increase their risk of exposure to botulinum toxin including diagnosed Myasthenia Gravis, Eaton-Lambert Syndrome, Amyotrophic Lateral Sclerosis or any other disease that might interfere with neuromuscular function.
9. Allergy or sensitivity to any component of BOTOX®