On February 8, 2007, the District of Columbia Department of Health (DCDOH) was notified of an outbreak of acute gastroenteritis in an elementary school (prekindergarten through sixth grade). The school nurse reported that 27 students and two staff members had become ill during February 4--8 with nausea, vomiting, and diarrhea; because symptoms lasted <48 hours, a viral etiology was suspected. DCDOH recommended two preinvestigation interventions, which were implemented the same evening (February 8): 1) more thorough handwashing and 2) bleach cleaning of all shared environmental surfaces with a diluted (1:50 concentration) household bleach solution. This report summarizes the subsequent investigation of the outbreak, which suggested that noncleaned computer equipment (i.e., keyboards and mice) and person-to-person contact resulted in illness. To decrease disease transmission during gastroenteritis outbreaks, public health officials should emphasize good handwashing practices, exclusion of ill persons, and thorough environmental disinfection, including fomites that are shared but not commonly cleaned.