Genetically modified pig hearts have been successfully transplanted into two brain-dead human recipients, marking a significant step forward in the development of pig-to-human heart xenotransplantation. The hearts functioned well for the duration of the 66-hour study, and there was no evidence of cellular or antibody-mediated rejection or zoonotic transmission. While more work is needed to advance this technology to human trials, these results suggest that pig-to-human heart xenotransplantation is possible and could one day offer a new solution to the shortage of human organs for transplantation.