The aim of this study was to assess whether acute myocardial infarction (AMI) in younger patients (< 45 years) differs from that in the older individuals (> 45 years). We have studied the records of all patients admitted to the Department of Medicine, Clinical Hospital of Split, Croatia, because of AMI from January 1st, 1987 to December 31st, 1991. The study group consisted of 1406 patients, 130 (9.2%) below, and 1276 (90.8%) above the age of 45. In the ¿young¿ subgroup there were only 9 females (6.9%), significantly less than in the ¿old¿ one (399 out of 1276 or 31.3%, p < 0.001). There were many more smokers among the younger (100 out of 130 or 76.9%) than among the older patients (524 out of 1276 or 41.1%, p < 0.001). The location of myocardial necrosis was also different: inferior infarction occurred in 65 out of 130 or 50% young patients and in 442 out of 1276 or 34.6% old patients; p < 0.001). Finally, the hospital mortality rate among the younger AMI patients was quite low (8 out of 130 or 6.2%) when compared to that of the older patients (282 out of 1276 or 22.1%, p < 0.001). In conclusion, AMI in younger individuals shows relevant peculiarities: the background of such patients almost invariably includes cigarette smoking; the female gender is about five times less affected, the diaphragmatic location is nearly two times more frequent, and the hospital mortality rate of these patients is almost four times lower than that of older patients.