Galactose- alpha 1, 3-galactose ( alpha 1,3Gal) is the major xenoantigen causing hyperacute rejection in pig-to-human xenotransplantation. Disruption of the gene encoding pig alpha 1,3-galactosyltransferase ( alpha 1,3GT) by homologous recombination is a means to completely remove the alpha 1,3Gal epitopes from xenografts. Here we report the disruption of one allele of the pig alpha 1,3GT gene in both male and female porcine primary fetal fibroblasts. Targeting was confirmed in 17 colonies by Southern blot analysis, and 7 of them were used for nuclear transfer. Using cells from one colony, we produced six cloned female piglets, of which five were of normal weight and apparently healthy. Southern blot analysis confirmed that these five piglets contain one disrupted pig alpha 1,3GT allele.