The etiology of acute lower respiratory tract infections (mostly pneumonia) in children is well characterized, but these are only some of the community-acquired infections warranting parenteral antimicrobial therapy. We prospectively evaluated all such infections among children aged 3 months to 15 years by use of blood cultures, examination of nasopharyngeal aspirates, and serologies for 15 viral, 7 bacterial, and 1 protozoal agent. Immunocompromised patients and those with urinary tract infection, meningitis, or osteoarticular infection were excluded. In all, 170 children were included. The pathogenic agent was identified in 62% of the cases. Bacteria were detected in 54%, and a pneumococcus was found in 59% of the cases identified. Viruses were found in 15% overall. Sole bacterial or viral infections were detected in 47.1% and 8.1%, respectively. Since thorough screening established the etiology in less than two-thirds of patients ill enough to be hospitalized and treated parenterally, better diagnostics are needed, especially to identify those who would truly benefit from antimicrobial therapy.