Overactive bladder (OAB) is a storage symptom complex that includes urinary urgency with or without urge incontinence, urinary frequency and nocturia. OAB is common symp- tom complex and its morbidity is high and increased with age. Although many factors cause OAB, we can classify them as neurogenic or non-neurogenic. To diagnose OAB, we need to ask a patient about his condition using Overactive Bladder Symptom Score (OABSS), exam- ine physical findings and urinalysis. And we also need to exclude other urinary tract diseases that make bladder irritation. Pharmacotherapy and behavior therapy are useful for improving OAB symptoms. Anticholinergic agents are utilized for OAB treatment but we need to pay attention to the adverse effects.