• Change from baseline to end of treatment in mean number of micturitions per 24 hours [ Time Frame: 12 Weeks ] [ Designated as safety issue: No ]
• Change from baseline to end of treatment in mean number of incontinence episode per 24 hours [ Time Frame: 12 Weeks ] [ Designated as safety issue: No ]

• Change from baseline in mean volume voided per micturition [ Time Frame: 12 Weeks ] [ Designated as safety issue: No ]
• Change from baseline in mean number of urgency incontinence episodes per 24 hours [ Time Frame: 12 Weeks ] [ Designated as safety issue: No ]
• Change from baseline in mean number of urgency episodes (grade 3 and/or 4) per 24 hours [ Time Frame: 12 Weeks ] [ Designated as safety issue: No ]

The study is intended to test the efficacy, safety and tolerability of two doses of YM178 against placebo to treat patients with symptoms of overactive bladder

• Drug: YM178
• Drug: Placebo

• Experimental: Low dose
• Experimental: Higher dose

Inclusion Criteria:

• Subject is willing and able to complete the micturition diary and questionnaires correctly
• Subject has symptoms of overactive bladder for >= 3 months
• Subject must experience frequency of micturition on average >= 8 times per 24-hour period during the 3-day micturition diary period
• Subject 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:

• Subject is breastfeeding, pregnant, intends to become pregnant during the study, or of childbearing potential, sexually active and not practicing a highly reliable method of birth control
• Subject has significant stress incontinence or mixed stress/urge incontinence where stress is the predominant factor
• Subject has an indwelling catheter or practices intermittent self-catheterization
• Subject has diabetic neuropathy
• Subject has evidence of a symptomatic urinary tract infection, chronic inflammation such as interstitial cystitis, bladder stones, previous pelvic radiation therapy or previous or current malignant disease of the pelvic organs
• Subject receives non-drug treatment including electro-stimulation therapy
• Subject has severe hypertension
• Subject has a known or suspected hypersensitivity to YM178, other ß-AR agonists, or any of the other inactive ingredients
• Subject has been treated with any investigational drug or device within 30 days
• Subject had an average total daily urine volume > 3000 mL as recorded in the 3-day micturition diary period
• Subject has serum creatinine of >150 μmol/L, or AST or ALT > 2x upper limit of normal range (ULN), or γ-GT > 3x ULN
• Subject has a clinically significant abnormal ECG