This invention provides a nonhuman transgenic mammal carrying transgene comprising the regulatory genes capable of functioning in the hyperacute rejection-occurring local cells and gene encoding human N-acetylglucosaminyltransferase III (GnT-III), or a nonhuman transgenic mammal carrying transgene comprising the regulatory genes and genes encoding GnT-III and the human complement inhibitor. Because of reduced .alpha.-Gal antigens in the hyperacute rejection-occurring local cells or because of both reduced .alpha.-Gal antigens and expression of the human complement inhibitor, the transgenic mammal of this invention can effectively inhibit the hyperacute rejection caused by discordant xenotransplantation. Consequently, this invention provides the transgenic mammal suitable for organ transplantation.