The present study was conducted to clarify the role of Respiratory syncytial virus (RSV) pneumonia in children. Seventy children at different age groups less than18 months were recruited in our study. They were admitted to Abu-Elrish El-mounira Paediatric Hospital during successive 3 years period where the following was done :1- Clinical examination for detection of pneumonia & bronchiolitis .2- chest x ray for confirmation Then nasopharyngeal aspirate collected from patients for 1- bacterialculture 2 -Nested revered PCR.