The human platelet antigens (HPA) are genetically defined polymorphisms expressed on platelet membrane glycoproteins. As platelet antigens are very important in several clinical situations and in population genetics, we used the polymerase chain reaction with sequence-specific primers (PCR-SSP) to investigate HPA-1, -2, -3 and -5 allele frequencies in the Croatian population. The HPA frequencies obtained in 219 Croatians were: 1a-0.854, 1b-0.146, 2a-0.890, 2b-0.110, 3a-0.575, 3b-0.425, 5a-0.895 and 5b-0.105. These data are similar to the frequencies reported in most European studies with some significant differences in HPA-2 when compared with the Dutch and German population, in HPA-3 when compared with the Swiss population and in HPA-5 when compared with the Finnish population. The three most common condensed HPA genotypes in the Croatian population were: HPA-1a/a, -2a/a, -3a/b, -5-a/a (0.283), HPA-1a/a, -2a/a, -3a/a, -5-a/a (0.137) and HPA-1a/b, -2a/a, -3a/b, -5-a/a (0.087). Data obtained in this study can be used for better understanding and treatment of immune-mediated platelet disorders in our population.