This study was performed to determine the usual duration of community-acquired viral upper respiratory tract infections and the incidence of complications (otitis media/sinusitis) of these respiratory tract infections in infancy and early childhood. Children in various forms of child-care arrangements (home care, group care, and day care) were enrolled at birth and observed for 3 years. Families were telephoned every 2 weeks to record on a standardized form the type and severity of illnesses experienced during the previous interval. Only children remaining in their original child-care group for the entire study period were compared. The mean duration of an upper respiratory tract infection varied between 6.6 days (for 1- to 2-year-old children in home care) and 8.9 days (for children younger than 1 year in day care). The percentage of apparently simple upper respiratory tract infections that lasted more than 15 days ranged from 6.5% (for 1- to 3-year-old children in home care) to 13.1% (for 2- to 3-year-old children in day care). Children in day care were more likely than children in home care to have protracted respiratory symptoms. Of 2741 respiratory tract infections recorded for the 3-year period, 801 (29.2%) were complicated by otitis media. During the first 2 years of life, children in any type of day care were more likely than children in home care to have otitis media as a complication of upper respiratory tract infection. In year 3, the risk of otitis media was similar in all types of child care.