During the period of air-raid alarms in Zagreb (September 1991), the influence of war-induced stress on the incidence and mortality of acute coronary artery disease was investigated. Control periods were September 1989 and September 1990. Among 2903 patients admitted to Emergency Care Units, 369 (13%) were examined for suspect acute coronary artery disease. During the same periods in 1989 and 1990, 10% and 11% of acute coronary artery disease patients were recorded, respectively. The percentage of patients with myocardial infarction or unstable angina, admitted to Coronary Care Units during September 1989, 1990 and 1991, was 49%, 50% and 55%, respectively. The number of Q myocardial patients admitted during September 1991 was significantly higher than that recorded during the same period in 1990. The incidence and mortality patterns in acute coronary artery disease patients were also examined during August, September and October 1991. The peak incidence of acute coronary artery disease was found in the first half of September, while the peak mortality in these patients was found during the second half of September. During the second half of September of 1989, 1990 and 1991, the mortality in Q myocardial patients in Coronary Care Units, was 16.7%, 15.2% and 23.8%, respectively. Besides the war-induced stress, transportation of our patients to shelters or inner parts of the hospital caused additional stress, probably contributing to the development of refractory malignant arrhythmia or heart failure.