The aim of the study was to determine the etiology of the viral bronchiolites in children by using direct immunofluorescence test and 3 RT-PCR Multiplex (S.Bellau-Pujol) The study was performed on 122 nasal inspirations collected from 3 weeks-6 month old children hospitalizated in the pediatrics service of CH Rouen. The results were that the majority (53%) of bronchiolites in children had like etiology RSV and a lot of these infections had double viral etiology (26% RSV+ Rhinovirus; 2,7% RSV+HMPV and 1% RSV+Coronavirus 229E). An important viral factor which gives bronchiolitis in children is HMPV (11%). We also find respiratory infections with triple viral etiology: RSV+Influenza A virus + Rhinovirus.