Objective: To investigate the role of vigorous physical exertion and anger as triggers of acute coronary syndromes(ACS) and to identify the clinical and sociodemographic correlates of triggering. Design: Prospective observational clinical cohort study. Setting: Four coronary care units in the London area. Patients: 295 men and women with electrocardiographically and biochemically verified ACS. Main outcome measures: Physical exertion in the 1 h and anger in the 2 h before symptom onset were assessed with structured interviews. Control periods were the equivalent hours one day earlier and usual rates over the past six months. Data were analysed by case-crossover methods. Results: Physical exertion was reported by 10%and anger by 17.4%of patients in the hazard period. The risk of ACS onset after physical exertion compared with light or no activity was 3.50(95%confidence interval(CI) 1.37 to 10.6). The risk of onset with anger was 2.06(95%CI 1.12 to 3.92). Physical exertion during the hazard period was related to an absence of premonitory symptoms, presentation with an ST elevation myocardial infarction(STEMI), low socioeconomic deprivation and higher future cardiovascular risk. Anger during the hazard period was more common in younger, socioeconomically deprived patients who presented with a STEMI. Conclusions: Triggers are relevant across the spectrum of ACS. The distinct clinical and sociodemographic factors associated with physical exertion and anger suggest that different pathophysiological processes may be involved. Objective: To investigate the role of vigorous physical exertion and anger as triggers of acute coronary syndromes (ACS) and to identify the clinical and sociodemographic correlates of triggering. Design: Prospective observational clinical cohort study. Setting: Four coronary care units in the London area Patients: 295 men and women with electrocardiographically and biochemically verified ACS. Main outcome measures: Physical exertion in the 1 h and anger in the 2 h before symptom onset were assessed with structured interviews. Control periods were the equivalent hours one day earlier and usual Results over the past six months. Data were analysed by case-crossover methods. Results: Physical exertion was reported by 10% and anger by 17.4% of patients in the hazard period. The risk of ACS onset after physical exertion compared with light or no Activity was 3.50 (95% confidence interval (CI) 1.37 to 10.6). The risk of onset with anger was 2.06 (95% CI 1.12 to 3.92). Physical exertion during the haz ard period was related to an absence of premonitory symptoms, presentation with an ST elevation myocardial infarction (STEMI), low socioeconomic deprivation and higher future cardiovascular risk. Anger during the hazard period was more common in younger, socioeconomically deprived patients who presented with a STEMI Conclusions: Triggers are relevant across the spectrum of ACS. The distinct clinical and sociodemographic factors associated with physical exertion and anger suggest that different pathophysiological processes may be involved.