Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease characterized by thrombocytopenia due to the presence of platelet autoantibodies specific for platelet membrane glycoproteins, such as GPIIb/IIIa, GPIb/IX and GPIa/IIa. These autoantibodies cause an accelerated clearance of opsonized platelets by phagocytes and inhibition of platelet production. Human platelet antigen (HPA) systems HPA-1, HPA-2, HPA-3 and HPA-5 are components of platelet GP complexes GPIIb/IIIa, GPIb/IX and GPIa/IIa. The HPA system consists of more than 12 bi-allelic antigen polymorphisms in which a base-pair substitution leads to change in an amino acid sequence of a membrane glycoprotein expressed on the platelet surface. The aim of this study was to examine the association of HPA-1, HPA-2, HPA-3 and HPA-5 polymorphisms with idiopathic thrombocytopenic purpura. We performed genotyping of HPA-1, HPA-2, HPA-3, and HPA-5 systems in 60 patients with ITP and 120 healthy participants. Genotyping of HPA-1, -2, -3, and -5 alleles were performed by PCR and RFLP methods by using specific primers and restriction enzymes. Allele and genotype frequencies of HPA-1, HPA-3, and HPA-5 were not significantly different between patients and healthy participants. After Bonferroni adjustment a significant association in ITP patients with HPA-2 alleles (P=0.015, OR=1.923, CI=1.126-3.284) was found. Allele frequencies for HPA-2a were 0.852 in healthy participants and 0.750 in patients, and for HPA-2b 0.148 and 0.250 respectively. These results suggests that HPA-2b allele was more frequent in patients with ITP and may be involved in the formation of a specific autoepitope.