Information is limited about national patterns of rotavirus infection throughout the USA. Discharge records and laboratory rotavirus detection for 1979-1989 at the Texas Children's Hospital, Houston, were evaluated to determine the impact of rotavirus gastroenteritis at a large children's hospital. The availability since 1983 of diagnostic assays less expensive than electron microscopy was associated with increased rotavirus detection. Only 67% of rotavirus-positive samples came from children likely to have had community-acquired acute gastroenteritis. Combined laboratory results and ICD-9 discharge diagnosis codes (008.6, 008.8, and 558.9) measured rotavirus activity better than either alone. A case definition for hospitalization for rotavirus infection resulted in an estimate that an average of 473 children were hospitalized for rotavirus infection at Texas Children's Hospital each year over the 10-year period. These cases accounted for 3.0% of all hospital days and $1.5 million per year in bed costs at this hospital. Hospitalization rates and the impact of hospital costs for the USA were estimated by extrapolation.