Study to Test the Efficacy and Safety of YM178 in Subjects With Symptoms of Overactive Bladder

Inclusion Criteria: * Patient is willing and able to complete the micturition diary correctly. * Symptoms of overactive bladder (urinary frequency and urgency with or without incontinence) for ≥ 3 months At randomization: * Patient must experience frequency of micturition on average ≥ 8 times per 24-hour period during the 3-day micturition diary period * Patient must experience at least 3 episodes of urgency (grade 3 or 4) with or without incontinence, during the 3-day micturition diary period Exclusion Criteria: * Pregnant women or women who intend to become pregnant during the study or women of childbearing potential who are sexually active and practicing an unreliable method of birth control or will be lactating during the study. Reliable contraceptive methods are intra-uterine devices, contraceptive pills of combination type, hormonal implants, contraceptive patches and injectable contraceptives * Clinically significant outflow obstruction (at the discretion of the investigator) * Significant post void residual volume (PVR\>200ml) * Significant stress incontinence or mixed stress/urge incontinence where stress is the predominant factor as determined by the investigator (for female patients confirmed by a cough provocation test) * Patients with a neurological cause for abnormal detrusor activity * Diabetic neuropathy * Evidence of a symptomatic urinary tract infection, chronic inflammation such as interstitial cystitis, bladder stones, previous pelvic radiation therap…