The pathogenic role of Kaposi's sarcoma associated herpesvirus or human herpesvirus-8 in the development of Kaposi's sarcoma is widely accepted today. Here the authors report an indirect immunofluorescence assay based seroepidemiologic study. Their results indicate that 1.56% (17/1089) of the Hungarian adult population and 100% (12/12) of Kaposi's sarcoma patients have serum antibodies to HHV-8 latent nuclear antigens.