A cDNA encoding a feline homologue of CD2 (fCD2) was identified. Several amino acids (aa) important for ligand interaction, molecular folding or signal transduction, found in other mammalian CD2, were found to be highly conserved in the predicted fCD2 aa sequence. fCD2-expressing cells were able to form rosettes with human red blood cells (probably via human CD58), and the rosette formation was inhibited by an anti-fCD2 monoclonal antibody. These results are indicative of the similarity of feline and human CD2 structures. fCD2 was found to be expressed in feline peripheral blood T lymphocytes, monocytes and cultured lymphoid cells.