To describe leading hypotheses surrounding the pathophysiology of overactive bladder (OAB), as well as describe the mechanisms of action of current treatment options for OAB. There are two main underlying mechanisms of OAB: mechanisms with increased sensory (afferent) activity and mechanisms with abnormal management of afferent signals. In the former category, increased afferent activity is thought to be related either to abnormalities in the urothelium receptor function and neurotransmitter release (urothelium-based hypothesis) or to abnormalities in myocyte excitability (myogenic hypothesis). In the latter category, OAB is thought to be related to the dysregulation of the handling of afferent signals (neurogenic hypothesis). OAB is complex and multifactorial in its etiology. Further research should be undertaken to better characterize the pathophysiology of the disorder, so that more targeted treatments can be developed.