The goal of this study was to determine the prevalence of DSM-III-R panic disorder and to describe its correlates.The study was part of the National Comorbidity Survey, the first psychiatric epidemiologic survey of the entire U.S. population and the first to use DSM-III-R criteria for diagnosis. The 8,098 survey respondents, aged 15-54 years, were given the Composite International Diagnostic Interview. For this report, the data on panic were analyzed, and from them the prevalence of panic disorder and related experiences in the U.S. population was estimated.About 15% of the survey respondents reported the occurrence of a panic attack over their lifetimes, and 3% reported a panic attack in the preceding month. About 1% met the DSM-III-R criteria for panic disorder in the month preceding the interview. Panic attacks and panic disorder had a bimodal age distribution and were associated with female sex and lower educational achievement. Fifty percent of the survey respondents with panic disorder reported no symptoms of agoraphobia. The pattern of prevalence of correlated sociodemographic factors was similar for persons with panic attacks, panic disorder, and panic disorder with agoraphobia.There appears to be no obvious threshold for the diagnosis of panic disorder. Panic disorder and agoraphobia, although highly comorbid, also occur separately.