Background: Galα1-3Gal epitopes (αGal) have been demonstrated to be present on tissues of all pig breeds tested to-date and are the major target for human anti-αgalactosyl (αGal) antibodies. We investigated members of an MHC-inbred miniature swine herd to assess whether there was an association between genotype and expression of αGal. Identification of a low expressor genotype would potentially enable selective breeding of pigs that might prove beneficial as donors in clinical xenotransplantation. Methods: we measured αGal expression on various pig cells by use of fluorescent-activated cell sorter (FACS) using (i) purified human anti-αGal antibody and (ii) the isolectin GS-I-B4. Initial studies were on porcine peripheral blood mononuclear cells (PBMCs) and subsequent studies on lymphocytes, platelets, and T cell subsets (CD4 + and CD8 + cells). Results: there was considerable day-to-day variation in αGal expression on PBMCs from the same pig. When only lymphocytes were examined, there was a high degree of reproducibility, and no significant difference in αGal expression was detected between representative pairs of animals of three different genotypes. Purified anti- αGal antibody bound to different sites on the αGal epitope than did Griffonia (Bandeiraea) simplicifolia I-B4 (GS-I-B4). Lectin binding was significantly reduced in the absence of divalent cations. When CD4 + and CD8 + T cells were examined for αGal expression, two distinct populations of each type of cell were observed, with larger cells expressing a higher level of αGal. Conclusions: although the number of pigs of different genotypes studied was small, on the basis of this limited study, pigs of a low αGal expressor genotype that could be selectively bred for use in clinical xenotransplantation were not identified.