The value of viral antigen detection from nasopharyngeal secretion (NFS) by enzyme immunoassay (EIA) in everyday clinical practice was evaluated in 570 children hospitalized because of infections. NPS-EIA gave a positive result in 32% of all cases. Virus isolation was positive in the NFS in 25%, virus isolation in stool samples in 14%, and virus serology in 28% of the cases. NPS-EIA was superior for detecting adenovirus, respiratory syncytial (RS) and parain-fluenza viruses. In a series of 124 patients in whom 3 methods were compared, NPS-EIA was the only positive method in 48% of all findings positive for adenoviruses, in 73% for RSV, and in 58% for parainfluenza viruses. Antigen detection by NPS-EIA markedly increased the diagnostic potential in everyday clinical practice, especially for viral respiratory diseases.