• Change from baseline to end of treatment in mean number of micturitions/24 h. [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
• Change from baseline to end of treatment in mean number of incontinence episodes/24 h. [ 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/24 h. [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
• Change from baseline in mean number of urgency episodes (grade 3 and/or 4) /24 h. [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]

The study is intended to test efficacy, safety and tolerability of two doses of YM178 against placebo and compare the efficacy and safety with active comparator in patients with symptoms of overactive bladder.

• Drug: YM178
• Drug: Tolterodine 4 mg
• 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 (urinary frequency and urgency with or without urge incontinence) for ≥ 3 months
• Subject experiences 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 tolterodine, other anticholinergics, YM178, other ß-AR agonists, or lactose or any of the other inactive ingredients
• Subject has been treated with any investigational drug or device within 30 days (90 days in the UK)
• Subject had an average total daily urine volume > 3000 mL as recorded in the 3-day micturition diary period
• Subject has serum creatinine >150 umol/L, AST and/or ALT > 2x upper limit of normal range (ULN), or γ-GT > 3x ULN
• Subject has a clinically significant abnormal ECG