Fecal and serum samples from a chimpanzee with acute-phase, blood-borne non-A, non-B hepatitis were administered to four chimpanzees. Fecal material given either intravenously or orally did not result in abnormal levels of alanine aminotransferase or the occurrence of ultrastructural alterations in hepatocellular cytoplasm characteristic of non-A, non-B hepatitis during a one-year period of follow-up. Definite non-A, non-B hepatitis was later demonstrated in two of these animals four weeks after inoculation of acute-phase serum. Thus, feces do not appear to transmit this human strain of blood-borne non-A, non-B hepatitis.