This study investigated the clinical features of immunocompetent children with adenovirus infection requiring hospitalization. The files of 78 children (mean age 17 ± 10 months) with community-acquired adenovirus infection admitted over a 2-year period were reviewed. The children were referred after 5.7 ± 3.4 days of illness, all with fever (mean peak 39.8 ± 0.8°C. Temperature normalized after 3.5 ± 2 days. Duration of hospitalization (mean, 7.0 ± 3.9 days) correlated with lethargy, lung crackles, cracked lips, hypoxia, impaired liver tests, and high serum lactic dehydrogenase (LDH) concentration at admission. Serum LDH concentrations and hypoxemia predicted 70% of the variance in hospital stay. All patients recovered. Adenovirus infection may cause considerable morbidity, even in immunocompetent children. Disease severity, defined by duration of hospitalization, correlates with serum LDH concentrations and oxygen saturation at admission.