Virus-like particles not previously described were observed in a human gastroenteritis stool using negative-stain TEM. The stool was among a number of acute-phase illness stools which had been collected in Egypt during 1980. The particles measured 65-70 nm in diameter, and it was possible to detect individual capsomers on many of these particles. The capsomeric pattern identified on the particles corresponded to an icosahedrally symmetric T = 19 capsid. Distinctive 5-fold vertices, usually appearing as darker spots on the capsid were an additional feature of these particles. The capsid structure, which is skew, could readily be distinguished from the T = 25 capsid of adenovirus and the holey capsids of rotavirus and reovirus. Antibody to the particles was detected in both the shedding individual's acute- and convalescent-phase serum specimens using IEM, although an antibody increase was not demonstrated.