OBJECTIVE This study sought to characterize the relative frequency, care, and survival of sudden cardiac arrest in traditional indoor exercise facilities, alternative indoor exercise sites, and other indoor sites. BACKGROUND Little is known about the relative frequency of sudden cardiac arrest at traditional indoor exercise facilities versus other indoor locations where people engage in exercise or about the survival at these sites in comparison with other indoor locations. METHODS We examined every public indoor sudden cardiac arrest in Seattle and King County from 1996 to 2008 and categorized each event as occurring at a traditional exercise center, an alternative exercise site, or a public indoor location not used for exercise. Arrests were further defined by the classification of the site, activity performed, demographics, characteristics of treatment, and survival. For some location types, annualized site incident rates of cardiac arrests were calculated. RESULTS We analyzed 849 arrests, with 52 at traditional centers, 84 at alternative exercise sites, and 713 at sites not associated with exercise. The site incident rates of arrests at indoor tennis facilities, indoor ice arenas, and bowling alleys were higher than at traditional fitness centers. Survival to hospital discharge was greater at exercise sites (56% at traditional and 45% at alternative) than at other public indoor locations (34%; p = 0.001). CONCLUSIONS We observed a higher rate of cardiac arrests at some alternative exercise facilities than at traditional exercise sites. Survival was higher at exercise sites than at nonexercise indoor sites. These data have important implications for automated external defibrillator placement.