A survey of the virological and epidemiological features of acute respiratory diseases in children admitted to hospital in Naples has been carried out; the results of three years of research are reported.Between April 1979 and March 1982, 787 nasopharyngeal swabs were examined. There were 287 (36.5%) positive samples, with the highest isolation rate being found in children with bronchiolitis (39.5%).Among the different viruses isolated, adenovirus was the most common (161 positive samples, 56%); this agent appeared regularly in the different age and disease groups, with a marked increase in prevalence during the winter of 1980. Isolations of herpesvirus, respiratory syncytial virus and enterovirus were less frequent; however, echovirus 3 caused an epidemic in the summer of 1980. Influenza and parainfluenza viruses were seen fairly infrequently; two cases of Reye's syndrome yielded strains of influenza B.