Objectives. The main aim of the study was to establish the association of genetic variants of the ARNTL1 gene with the onset of myocardial infarction. Study design. Case-control study Participants and Methods. Our research is conducted on a total of 400 people. In the first group there were 200 patients with myocardial infarction type 1 treated at Clinical Hospital Center Osijek. The second group consisted of 200 healthy persons recruited by a family physician. The goal of the study was to determine the correlation between single nucleotide polymorphisms of ARNTL1 gene and myocardial infarction. All subjects were genotyped into three polymorphisms of the ARNTL1 gene (rs3789327, rs4757144, rs12363415). Results. There was no statistically significant difference between polymorphisms of ARNTL1 gene in patients and controls. Research has shown that there is no direct link between infarction and single nucleotide polymorphisms of the ARNTL1 gene, but rs3789327 and rs12363415 polymorphisms are associated with risk factors for the development of acute complications. These are diabetes mellitus type 2 for rs12363415 polymorphism and previous diagnosis of cardiovascular diseases for rs3789327 polymorphism. Type 2 diabetes mellitus is an important risk factor because it is associated with the development of atherosclerosis and coronary artery disease. Conclusion. The results show that there is no direct link between SNP's of ARNTL1 gene and myocardial infarction. The association of SNPs and risk factors in the development of the infarction was found. Based on this, the polymorphism of the ARNTL1 gene has a certain role in the emergence of myocardial infarction Key words: ARNTL1 gene; circadian rhythm; myocardial infarction