Candida albicans is a leading cause of disseminated fungal infection in immunocompromised patients. Candida-host cell interactions are mediated at the cell surface. Since blood-group I epitopes have been detected on the surface of C albicans cells, we investigated whether CD45, the molecule that carries the I antigen on human lymphocytes, is present on the C albicans cell surface, in culture and in human tissue specimens of human candidiasis. By using monoclonal antibodies to CD45, CD45RO, and CD45RA, we found a strong immunoreactivity at the cell surface of blastoconidia bearing germ tubes but weak or no immunostaining of the germ tubes themselves. In human tissues, immunostaining of C albicans yeast cells was detected, whereas pseudohyphae were mostly negative. CD45 epitopes on the surface of C albicans might have a role in tissue invasion and dissemination of the fungus. On the other hand, its detection may disturb quantitative non-morphology-based determinations of lymphoid cell populations in infected tissues.