OBJECTIVE To examine the effects of war in Bosnia and Herzegovina on the occurrence of acute coronary syndrome among civilians. METHODS The incidences of acute myocardial infarctions (first and recurrent) and unstable angina pectoris were examined among the residents of Mostar and the nine neighboring districts. The study population was the population that lived in the area before the war (182,000 in the 1991 census). Others who immigrated into the area were not taken into consideration. Five consecutive years (1987-1991) before the war and 5 consecutive years (1992-1996) during the war were analyzed. RESULTS In the 5-year period during the war, 267 men and 161 women suffered from acute myocardial infarctions, compared with 246 men and 119 women in the 5-year period before the war. The wartime increase in acute myocardial infarctions for the combined male-female population was statistically significant (p = 0.025). For women, the wartime increase was statistically significant only for the age group of 60 to 69 years (p = 0.007). The smaller increase among men was not statistically significant (p = 0.354). The increase to a wartime number of 52 cases of recurrent myocardial infarctions from a prewar level of 24 was statistically significant (p = 0.001). The percentage of fatal myocardial infarctions among women, however, was lower during the war (18.6%) than before the war (32.8%) (p = 0.048). During the war, 109 men with unstable angina pectoris were hospitalized, compared with 84 before the war; the cases among women were 76 and 41, respectively. The increase was statistically significant among women (p = 0.001) but not among men (p = 0.072). There was a statistically significant increase (p < 0.001) in the total number of unstable angina pectoris cases during the war (185 cases, compared with 125 prewar cases). CONCLUSION The common population during the war in Bosnia and Herzegovina had increased numbers of acute myocardial infarctions and unstable angina pectoris cases.