The epidemiology of the small round-structured virus, Mexico virus (MxV), was investigated in North and West Yorkshire, United Kingdom, between January 1992 and March 1995 using a typespecific antigen ELISA. The results indicate that an epidemic of MxV occurred during the winter of 1993–1994, when this strain was associated with 45 of 99 outbreaks and sporadic childhood cases of gastroenteritis. Only 4 MxV-like isolates were found during the 1992–1993 winter season and none in the 1994–1995 season. This descriptive epidemiologic study suggests that MxV has an epidemic pattern of infection.