Over 200 strains of respiratory viruses cause a variety of human infections ranging from common cold to life-threatening pneumonia. Respiratory viruses implicated in this study are respiratory syncytial viruses (RSV), adenovirus, influenza viruses and parainfluenza viruses. The objective of this study is to determine the epidemiology of respiratory viruses in paediatric patients with lower respiratory tract infection. The methods used were direct antigen detection method, shell vial culture method and conventional tube culture method. The samples included in this study are paediatric patients seen in Universiti Kebangsaan Malaysia Hospital, Kuala Lumpur with suspected acute viral respiratory infection, presenting with acute laryngotracheobronchitis (croup), bronchiolitis and pneumonia. Nasopharyngeal aspirates were collected and processed almost immediately. A total of 222 specimens were received during February 1999 to January 2000 showing a dual peak pattern in the months of April and December. The mean age of the patients was 13 months. Pneumonia (77.9%) was the most common clinical diagnosis in children with lower respiratory tract infection. This was followed by bronchiolitis (19.4%) and croup (27%). Viral aetiologies were confirmed in 23.4% of the patients. The most common respiratory virus isolated or detected was RSV, followed by parainfluenza viruses, influenza viruses and adenovirus.