A total of 383 cases of incident panic attack were identified among 12,823 participants in the Epidemiologic Catchment Area Program over various 12-month periods in 1980-1983. These cases not phobia-stimulated were compared with 766 controls. Risk factors were examined for the onset of panic attacks, with attacks categorized as panic disorder, severe and unexplained panic attacks, or other panic attacks. Risk factors were also examined for the onset of attacks in which cardiovascular symptoms were experienced and those in which psychologic symptoms were experienced. Females were at greater risk than males for each category of attacks (relative odds ranged from 1.36 to 2.25). Persons aged 65 years or older were at lower risk than younger persons (relative odds, compared with 30- to 44-year-olds, ranged from 0.26 to 0.71). A history of cardiac symptoms, shortness of breath, depression or a major grief episode, drug abuse or dependence, alcohol abuse or dependence, and seizures were each strongly associated with panic attacks. A history of cardiac symptoms was more strongly associated with attacks in which cardiovascular symptoms were experienced than with attacks in which psychologic symptoms were experienced (relative odds, 8.36 vs. 2.23). A history of seizures was more strongly associated with attacks with psychologic symptoms than with attacks with cardiovascular symptoms (relative odds, 5.21 vs. 1.58).