This paper examines the hypothesis that latent murine cytomegalovirus (MCMV) may be transmitted in kidney tissue to transplant recipients. Balb/c mice were infected with MCMV, and at intervals of less than 1 week to greater than 1 year, transmission of the virus from infected donors was attempted by transplantation of kidney sections or transfusion of blood into uninfected recipients. Graft recipients were killed from 2-4 weeks later, and cultured for MCMV. Restriction endonuclease digestion profiles of viral DNA were performed. Acutely infected donors transmitted MCMV in kidney tissue to 83-66% of untreated, susceptible recipients. Latently infected donors transmitted the infecting strain of virus to 20% of all and 31% of immunosuppressed recipients but to 37% of the syngeneic versus 21% of the allogeneic (P less than .027). Blood transfusions transmitted latent virus to 28% of recipients. In conclusion, kidney tissue may serve as the source of latent virus in this murine transplantation model. Retained blood in the kidney is unlikely to be the only source of virus.