Newly available molecular tools allow a sensitive detection of a broad panel of viruses in respiratory tract specimens. In the present study, the application of a multiplex RT-PCR DNA microarray in diagnosis and epidemiological survey of viral infections in infants hospitalized for bronchiolitis was assessed. One hundred and thirty-eight nasopharyngeal aspirates collected from October 2007 to September 2008 were tested by direct immunofluorescence and viral culture, a combination of referenced RT-PCRs and the DNA microarray. One or more viruses were detected in 96, 126 and 126 of the specimens by direct immunofluorescence and viral culture, RT-PCRs and DNA microarray, respectively (70 vs. 91 vs. 91%, P < 10−3). The RT-PCRs and the DNA microarray yielded concordant results for 99% of specimens and identified mixed viral infections in 85 (62%). The most common associations were: human bocavirus and respiratory syncytial virus (32%), adenovirus and respiratory syncytial virus (30%), and parainfluenza virus type 3 and respiratory syncytial virus (23%). None of the bronchiolitis severity parameters including intensive care unit admission, O2 supply, O2 saturation percentage, O2 length and length of stay at the hospital appeared to be significantly increased in multiple viral infections compared to single viral infections (P > 0.1). In conclusion, the use of this DNA microarray in clinical virology practice allows rapid and accurate identification of common and uncommon viral respiratory pathogens in infants hospitalized for bronchiolitis. It should improve the clinical management, the epidemiological survey, and the prevention of the nosocomial transmission of respiratory viruses in pediatric wards. J. Med. Virol. 84:979–985, 2012. © 2012 Wiley Periodicals, Inc.