Background and purpose: Major histocompatibility antigens are the most polymorphic components of the immune system. The purpose of this study was to determine the frequency of human leukocyte antigens (HLA) in a population in Mazandaran province, Iran. Materials and methods: In a cross sectional study, peripheral blood samples were obtained from 550 people in Immunogenetics Research Center affiliated with Mazandaran University of Medical Sciences, 2016-2021. The types of HLA class 1 antigens (A-B-C) were studied using SSP-PCR. Results: HLA-A * 24, HLA-B * 35 and HLA-C * 04 were found to be the most common alleles in the population studied. Conclusion: HLA diversity plays a major role in developing some diseases. So, it should be investigated in anthropological studies and finding a suitable donor in bone marrow transplantation. In fact, more extensive studies are required to draw a new horizon in the association between HLA and diseases in different ethnicities.