The purpose of this white paper is to recommend the minimum reporting standards for pathologic characterization of kidney and heart xenografts in humans. This proposal is based on the current human classifications for kidney and heart allografts, with additions and caveats relevant to xenografts that are primarily based on non-human primate and a limited number of organ xenografts in decedent and living humans. Such recommendations should not be regarded as diagnostic criteria, given that many new pathologic patterns and mechanisms remain to be fully characterized. While xenograft transplantation continues to evolve, this report serves as groundwork and an initial step towards defining international standards in xenograft histopathology assessment and reporting. Note: The authors welcome comments from the international transplantation community through the AJT Banff Blog: https://amjtransplant.wixsite.com/ajtbanffblog