Objective: We retrospectively evaluated the incidence of detrusor overactivity (DO) in uncomplicated overactive bladder syndrome (OAB) patients. Methods: From December 1993 to October 2003, 139 adult patients were referred to an urodynamic clinic for urodynamic evaluation of frequency and/or urinary incontinence. Of these, 50 patients (12 males and 38 females) with urgency, without any overt pathological conditions, were retrospectively evaluated in regard to patient age, storage symptoms, urodynamic parameters, and the presence or absence of DO (DO patients or no DO patients, respectively). Results: The overall incidence of DO was 75% (nine of 12 patients) and 36.8% (14 of 38 patients) in male and female patients, respectively. Two of nine male DO patients and five of 14 female DO patients revealed DO after provocative maneuvers. In male patients, all DO patients were OAB wet. In female patients, 13 of 14 DO patients were OAB wet (92.9%), whereas 17 of 24 no DO patients were also OAB wet (70.8%). Compared with no DO patients, female DO patients revealed statistically significant lower maximum cystometric capacity (P = 0.0139) and lower vesical compliance (P = 0.0002). Although aged 60 years or more was associated with DO in univariate analysis in female patients, any symptoms, even incontinence, were not associated with DO in both sexes. Conclusion: It is supposed that, in contrast to male OAB, DO might not be a major underlying cause of uncomplicated female OAB.