The National Overactive BLadder Evaluation (NOBLE) Program was initiated to better understand the prevalence and burden of overactive bladder in a broad spectrum of the United States population. Objective: To estimate the prevalence of overactive bladder with and without urge incontinence in the US, assess variation in prevalence by sex and other factors, and measure individual burden. Design: US national telephone survey using a clinically validated interview and a follow-up nested study comparing overactive bladder cases to sex-and age-matched controls. Setting: Noninstitutionalized US adult population. Participants: A sample of 5,204 adults ‡18 years of age and representative of the US population by sex, age, and geographical region. Main outcome measures: Prevalence of overactive bladder with and without urge incontinence and risk factors for overactive bladder in the US. In the nested case-control study, SF-36, CES-D, and MOS sleep scores were used to assess impact. Results: The overall prevalence of overactive bladder was similar between men (16.0%) and women (16.9%), but sex-specific prevalence differed substantially by severity of symptoms. In women, prevalence of urge incontinence increased with age from 2.0% to 19% with a marked increase after 44 years of age, and in men, increased with age from 0.3% to 8.9% with a marked increase after 64 years of age. Across all age groups, overactive bladder without urge incontinence was more common in men than in women. Overactive bladder with and without urge incontinence was associated with clinically and significantly lower SF-36 quality-of-life scores, higher CES-D depression scores, and poorer quality of sleep than matched controls. Conclusions: the NOBLE studies do not support the commonly held notion that women are considerably more likely than men to have urgency-related bladder control problems. The overall prevalence of overactive bladder does not differ by sex; however, the severity and nature of symptom expression does differ. Sex-specific anatomic differences may increase the probability that overactive bladder is expressed as urge incontinence among women compared with men. Nonetheless, overactive bladder, with and without incontinence, has a clinically significant impact on quality-of-life, quality-of-sleep, and mental health, in both men and women. Overactive bladder (OAB) is a common disabling condition that affects health-related quality of life (HRQL) [1]. Estimates of the prevalence and related social burden of OAB vary widely, in part due to variation in the assessment of symptoms, the populations surveyed, the methods used to collect data, and the criteria used to define OAB. Recently, the International Continence Society (ICS) derived a consensus symptomatic definition of OAB as urinary urgency, with or without urge incontinence, usually with urinary frequency and nocturia, in the absence of pathologic or metabolic factors that would