The authors report 57 cases of Respiratory Syncytial Virus (RSV) lower respiratory tract infection. The diagnosis was performed by detection of specific serum antibodies of IgM class or by direct detection of RSV antigens in nasopharyngeal specimens. Most of the patients were younger than one year. No one had risk factors for severe RSV infection form. All patients recovered. The authors emphasize the difficulties to discriminate between bronchiolitis and interstitial pneumonitis on the basis of the clinical and radiological features.