Frequency of promoter endothelial NO-synthase gene allelic polymorphism by using polymerase chain reaction and restriction fragment length polymorphism (RFLP-PCR) was determined in 221 patients with acute coronary syndrome (ACS) and in 83 almost healthy subjects. Data obtained indi- cate that different promoter allelic variant frequency differs significantly in patients with ACS and in control group. Correlation of normal homozygotes (Т/Т), heterozygotes (Т/С) and pathologic homozysotes (С/С) was 48%, 36% and 16% respectively in patients, and in control it was 48%, 46%, 6% (Р<0.05 by c2-test). Thus, in patients with ACS in Ukrai- nian population pathologic С/С variants of 5’- flanking region of eNOS gene were found 2.7-times more often in ACS pa- tients, than in control. This allows us to suggest, that this allelic polymorphism can be considered as one of genetic risk factors of ACS development.