Viral respiratory infections are common causes of illness in infants and children. Examination of clinical specimens submitted for diagnosis during a 3-year period (August 1993-July 1996) at King Faisal Specialist Hospital and Research Center (KFSH & RC) in Riyadh revealed a wide spectrum of diseases associated with the isolation of five respiratory viruses. Severity of disease ranged from mild upper respiratory illness to threatening lower respiratory illnesses including bronchiolitis and pneumonia. Of the 256 isolates, respiratory syncytial virus (RSV) accounted for 73 (28.5%), adenoviruses for 70 (27.3%), influenza viruses for 61 (23.8%), enteroviruses for 39 (15.2%) and para-influenza for 13 (2.3%). Viruses were found more frequently in children attending emergency or paediatric wards than in outpatients. RSV appears in November and the seasonal peak occurs during January and February. Influenza activity begins in September and peaks in November and December. Para-influenza type I emerges in winter and para-influenza type III follows the influenza epidemic and may be detected sporadically in summer. The other viruses (enteroviruses, adenoviruses) were isolated throughout the year.