Virus-like particles (VLPs) with a mean diameter of 32 nm were recovered from the stools of three acute phase cases of enterically transmitted non-A, non-B hepatitis (ET-NANBH) occurring in the Soviet Union, North Africa and North America. VLPs from two of these cases were studied in detail and were shown to react specifically with antibody in acute phase sera obtained from other cases of ET-NANBH in Asia, the Soviet Union, North Africa and North America. Partially purified VLPs were found to sediment at 183S in sucrose gradients and to cross-react with antibody in acute phase sera from geographically isolated cases of ET-NANBH. The latter virus preparations were also used to document the seroconversion of experimentally ET-NANBH-infected cynomolgus macaques to 32 nm VLPs. Our findings indicate that one virus or class of viruses is responsible for the majority of ET-NANBH.