Serotype distribution of group A rotavirus in children attending day care centers has not been previously reported. Fifteen centers in Houston participated in longitudinal monitoring of rotavirus infection during one to three consecutive rotavirus seasons. Monitoring included daily recording of the presence of diarrhea and weekly stool collection. Stool specimens containing rotavirus were analyzed by a monoclonal antibody (MAb)-based ELISA specific for the VP7 protein of serotypes 1, 2, 3, and 4 and by gel electrophoresis. A total of 318 children had 362 rotavirus episodes; 149 could be serotyped. Serotype distribution of this population was similar to that of children hospitalized for diarrhea in a large pediatric hospital in Houston during the same period. Symptomatic infections were predominantly due to serotype 1 rotaviruses in season 2 and serotype 3 rotaviruses in season 3. Episodes recurred in 43 children; 2 children had second symptomatic infections of the same serotype as the first. Electrophoretic differences among rotaviruses of a same serotype were common and more frequent among serotype 1 than serotype 3 viruses.