Laboratory reports and data on hospital admissions were used to estimate the number of hospitalizations due to group A rotavirus infection in England and Wales. Between January 1990 and December 1994, there were 75,059 laboratory reports of rotavirus infection, and 66,062 of these were in children <5 years old; rotavirus represented 39% of all pathogens identified in fecal specimens from this age group. Between April 1993 and March 1994, 1904 hospital admissions coded as "infectious intestinal disease" and 2354 coded as "noninfective gastroenteritis" occurred in children <5 in the North Thames region (a health authority representing 13% of the population in England and Wales). By modeling admission and laboratory reporting data, it was estimated that 54% of hospitalizations for intestinal infectious disease and 34% for noninfective gastroenteritis were attributable to rotavirus. By extrapolation of the North Thames data, it was estimated that 17,810 rotavirus-related hospitalizations (5/1000 children <5 years old) occurred in England and Wales during the same period. Effective vaccines have the potential to substantially reduce the number of hospital admissions due to group A rotavirus infection.