The frequency of occurrence and etiology of respiratory disease during a 40-month period in a day care center is reported. The day care center had a maximum enrollment of 39 children ranging in age from 1 month to 5 years. Sick children were not excluded from the center. During the period of the study there was not an excessive amount of respiratory illness in the children in day care when compared with the reported illness occurrence in children receiving home care. In the total group there were 8.4 respiratory illnesses per child-year with the highest rate in infants under 1 year of age. The agents responsible for the respiratory disease in the day care center were similar to those reported as significant in the community, and the patterns of virus isolation were similar to those in the community in age incidence, seasonal occurrence, and illness association. Respiratory syncytial virus and parainfluenza virus type 3 were the agents most often implicated in lower respiratory disease. Adenovirus types 2 and 5 frequently caused febrile upper respiratory illness in infants. The study suggests group day care is safe medically for infants and that exclusion of sick children is unnecessary in a day care program with adequate space and staffing.