Viral particles morphologically resembling animals caliciviruses in the faeces of a patient with acute gastroenteritis were purified, radiolabeled with [125I], and analyzed by SDS-PAGE. A single major structural protein with a mol. mass 62,000 daltons was identified by immunoprecipitation technique. The finding is consistent with human calicivirus-like particles associated with gastroenteritis being a member of the family Caliciviridae.