Non-A, non-B hepatitis was transmitted to eight chimpanzees by intravenous inoculation with antihemophilic materials (factor VIII) that had been implicated in transmission of the disease, with acute-phase liver homogenate from an infected chimpanzee, with acute-phase from an infected chimpanzee, or with chronic-phase plasma from infected chimpanzees. All eight animals developed elevated alanine aminotransferase activity, and all demonstrated unique hepatocyte cytoplasmic tubules at some time during the acute phase of disease. The temporal patterns for tubule appearance in hepatocyte cytoplasm, however, were highly variable, even between chimpanzees given similar inocula. Convoluted membranous structures were found occasionally in early or pre-acute-phase liver biopsy specimens. Aggregates of microtubules were also found in hepatocyte cytoplasm in some acute-phase biopsy specimens. No disease-specific nuclear changes or structures, including clusters or crystalline arrays of virus-like particles, were found in any of the serial liver biopsy specimens from chimpanzees with experimental non-A, non-B hepatitis.