A new ultrastructural cytoplasmic marker designated as type 2, and distinct from type 1 previously associated with NA-NB hepatitis in chimpanzees, was found in hepatocytes of two patients and of one experimentally infected chimpanzee. These cases represent a minority of all cases we studied as presumed NA-NB viral hepatitis. Type 2 marker consists of tubular structures composed of an assembly of ring-like units coated with smaller uniform fragments, accumulated in different patterns in dilated cisternae of the endoplasmic reticulum. Preliminary data using immunofluorescence with NA-NB hepatitis convalescent serum and antiserum against fibrinogen are reported. Type 2 marker may represent a different agent or a different reaction pattern to one agent of NA-NB viral hepatitis. Its features are compared with those of hepatitis B.