Gal alpha 1,3Gal (Gal) is the first target in antibody-mediated rejection of pig-to-non-human primate xenograft. Its expression may vary between organs and constituents of organs. Gal expression was studied in pancreas, testis, spleen and thymus of 22 pigs, with ages ranging from 1 to 22 months. The immunoperoxidase technique using the biotinylated lectin, Griffonia simplicifolia (IB4), was used. In the pancreas, neither endocrine (islet cells) nor exocrine cells expressed Gal. The Sertoli cells in the testis were negative. The spleen capsule and trabeculae did not stain for Gal, although both splenic T and B lymphocytes expressed Gal (B > T). Thymocytes were weakly positive, whereas thymic epithelial cells were negative for Gal. No age-related differences were seen in any tissues. Porcine islets of Langerhans, Sertoli cells, and the splenic and thymic structural frameworks did not express Gal, and therefore, should be relatively resistant to anti-Gal antibody-mediated rejection. The availability of pigs deficient in Gal as a source of islets may therefore not be beneficial in extending islet graft survival in non-human primate models.