Previous studies have shown that an acute coronary syndrome (ACS) may be triggered by external activities; however, their frequency, predictors, and significance are uncertain. We evaluated data from the National Israel Survey of Acute Coronary Syndromes, which was conducted in 2004 (February to March) in all 25 coronary care units and cardiac wards in Israel. Demographic and clinical data were recorded for consecutive participants, including potential triggers and time of symptom onset of ACS. Among the 1,849 patients who completed the trigger question, 1/4 (25.9%) reported a possible trigger, comprising heavy physical exertion (15.2%), emotional stress (8.3%), anger (1.1%), heavy meal (1.3%), and sexual activity (0.5%). Predictors of a triggered ACS were age <65 years, previous angina, no previous angiotensin-converting enzyme inhibitors/angiotensin 2 receptor blockers, impaired functional class, not having typical chest pain on admission, and a final diagnosis of unstable angina. The highest proportion of triggered ACS was between noon and 6 P.M. Physical exertion as a trigger was associated with reduced in-hospital mortality (0.4% vs 2.8%, p <0.05) and 1-year mortality. Emotional stress as a trigger did not influence in-hospital or 1-year mortality; however among those discharged from hospital, it was associated with increased 30-day rehospitalization (27.6% vs 19.3%, p <0.05) and a trend toward increased mortality (4.1% vs 2.0%, p = 0.10).