Clinical manifestations of respiratory tract infection often precede or coincide with rotavirus gastroenteritis in infants and children. To investigate the possible association between respiratory tract manifestations and rotavirus infection, the authors determined human rotavirus (HRV) antigen and respiratory syncytial virus (RSV) antigen in tracheal aspirates of 58 children with clinically diagnosed pneumonia by enzyme-linked immunosorbent assay (ELISA) and immunofluorescent antibody techniques. HRV antigen was detected in 16 out of the 58 cases (27.6%) and RSV antigen was found positive in 27 cases (46.5%). In four cases both HRV and RSV antigens were detected. The results of our study suggest that rotavirus may occasionally by one of the etiologic agents of acute lower respiratory infections of infants and children and that rotavirus infection may be transmitted via respiratory route. However, further extensive studies are needed for confirmation of the association between rotavirus and respiratory tract infection.