Purpose: To evaluate the risks and benefits of pet ownership by immunodeficient patients, focusing primarily on organisms that colonize animals and are transmitted to humans. Those diseases that are known to be progressive or more severe in patients with altered immune function are emphasized.; Methods: A review of the medical and veterinary literature pertaining to zoonoses transmitted by domestic animals was completed. Information pertaining to issues involving immuno-suppressed patients including AIDS was carefully evaluated and summarized for inclusion.; Results: There are significant clinical and psychosocial benefits to pet ownership. However, numerous diseases can be acquired from these animals which may be more severe in immunocompromised individuals.; Conclusion: Simple guidelines for pet ownership by immuno-suppressed patients can be implemented to reduce their risk of disease and allow them to safely interchange with their pets.