Overactive bladder (OAB) syndrome is a condition that involves urinary urgency, usually accompanied by increased daytime frequency and nocturia, with or without urgency urinary incontinence, in the absence of urinary tract infection or other obvious pathology. This condition is multifactorial, and several theories exist that explain the pathophysiologic process underlying the condition. Because the prevalence of the condition is high among women across all age groups, obstetrician-gynecologists will encounter women with OAB syndrome and should be able to evaluate and treat this condition. The appropriate management often is based on the degree of bother and severity of symptoms in an individual patient. This monograph will delineate the general characteristics of OAB syndrome from its epidemiology to potential causes and provide a detailed discussion of the evaluation of the patient with various diagnostic modalities and the range of available treatment options.