This study retrospectively reviewed those pediatric patients of acute lower respiratory tract infection with positive virus identification by direct immunofluorescence assay (Direct IF) from Jan, 1992 to Dec, 1993. One hundred and eighteen patients with 133 positive Direct IF results (107 cases with single virus identified, and 11 cases with more than one) were included. The sex ratio was 1.6:1 with males predominant; age, 22.1 (1 approximately 154.8) (months); duration of admission, 5.7 (1 approximately 69) (days); peripheral white blood cell count, 10,600 +/- 3,800/mm3; C-reactive protein, 17.0 (0 approximately 163.3) mu/ml; body temperature, 37.1 +/- 1.1 degrees C in those cases with single virus. The symptoms were cough 105 cases (98.1%), rhinorrhea 46 cases (43.0%), dyspnea and/or tachypnea 43 cases (40.2%) and diarrhea 15 cases (14.0%). The viruses identified were: Adenovirus (52 cases, 39.1%). Influenza B (45 cases, 33.8%), Parainfluenza 1 (28 cases, 20.1%), Parainfluenza 3 (19 cases 14.3%), Respiratory Syncytial virus (17 cases, 12.8%), and Influenza A (9 cases, 6.8%). The seasonal incidence rates were spring (49 cases, 36.8%), summer (46 cases, 34.6%), autumn (23 cases, 17.3%), and winter (15 cases, 11.3%). The results showed much similarity with others, except the commonest viral type (Adenovirus in this study; Respiratory Syncytial virus in others) and the seasonal incidence rate (higher in spring and summer in this study but not in others). In conclusion, most children with acute viral lower respiratory tract infection had an uneventful course and Direct IF is a reliable method for viral detection in that disease.