Acute respiratory infection is a significant cause of morbidity and mortality in children worldwide. Accurate identification of causative agents is critical to case management and to prioritization in vaccine development. Sensitive multiplex diagnostics provide us with an opportunity to investigate the relative contributions of individual agents and may also facilitate the discovery of new pathogens. Recently, application of MassTag polymerase chain reaction (PCR) to undiagnosed influenza-like illness in New York State led to the discovery of a novel rhinovirus genotype. Here we report the investigation, by MassTag PCR, of pediatric respiratory-tract infections in Germany, studying 97 cases for which no pathogen was identified through routine laboratory evaluation. Respiratory viruses were identified in 49 cases (51%); of the 55 identified viruses, 41 (75%) were rhinoviruses. The novel genotype represented 73% of rhinoviruses and 55% of all identified viruses. Infections with the novel genotype were associated with upper-respiratory-tract symptoms but, more frequently, with bronchitis, bronchiolitis, and pneumonia.