Rhinovirus is an important cause of respiratory infection among all age groups, but it is primarily thought of as being responsible for upper respiratory tract infection. Rhinovirus was isolated from the respiratory tract of 48 pediatric patients who were hospitalized (40) or seen in a pediatric emergency room (8) during the period of July, 1985, through December, 1988. Twenty-eight (58%) of the patients presented during the spring and early summer. Forty-one (86%) of the 48 patients were less than 12 months of age. All except four of the patients had viral cultures performed because of respiratory symptoms. Bronchiolitis was the single most frequent clinical diagnosis and was noted in equal proportion among children less than 3 months and 3 to 12 months of age. Nine patients were assigned a diagnosis of suspected sepsis. Rhinovirus infection was a complication of underlying illness for 17 (44%) of the 40 hospitalized patients, and those patients tended to be older than the otherwise healthy hospitalized infants with rhinovirus. Twenty-six patients (54%) were treated with antibacterial agents, although only one patient was documented to have a concomitant bacterial infection (Chlamydia trachomatis). Overall rhinovirus isolation during the study period represented 0.7% of all specimens submitted for viral isolation compared with 8.2% for respiratory syncytial virus. Rhinovirus infection leads to hospitalization less frequently than does respiratory syncytial virus infection, but the severity of illness and clinical presentation in young infants are similar.