We examined the localization of human blood antigen H (AbH) and its correlation with other cell type markers in the taste buds of circumvallate papillae of the adult rat. Immunoreactivity for AbH was localized in the membrane of two cell populations in the taste buds: in spindle-shaped cells extending from base to the apical portion of the taste buds as well as in round-shaped cells at the basal portion of the taste buds. Quantitative analysis revealed that approximately 47.8%, 24.4%, and 14.6% of cells within the taste buds displayed AbH-, alpha-gustducin- or protein gene product 9.5 (PGP 9.5)-immunoreactivity, respectively. Approximately 16.3% and 6.6% of AbH-immunoreactive taste bud cells displayed alpha-gustducin- or PGP 9.5-immunoreactivity, respectively. Although previous studies proposed that AbH immunoreactivity was specific for type I cells (dark cells or supporting cells), the present results indicate that AbH immunoreactivity is also present in some type II cells (alpha-gustducin immunoreactive cells) and type III cells (PGP 9.5-immunoreactive cells).