Respiratory syncytial virus (RSV), the most important cause of lower respiratory disease in infants and young children, is rarely considered among the causes for community-acquired lower respiratory infection in adults. All noninstitutionalized adults hospitalized with community-acquired pneumonia in two Ohio counties were evaluated between December 1990 and May 1992. Fifty-three (4.4%) of 1195 adults admitted during the RSV seasons and 4 (1.0%) of 390 in the off-season had serologic evidence of RSV infection, making RSV one of the four most common pathogens identified. RSV-infected patients had clinical features (e.g., wheezing and rhonchi) that distinguished them from all non-RSV-infected patients and other features (e.g., nonelevated white blood cell counts) that distinguished them from those infected with bacterial or atypical agents. However, RSV infection was not diagnosed during hospitalization for any of the 57 RSV-infected patients. RSV should be considered in the differential diagnosis for adults hospitalized between November and April with community-acquired lower respiratory infection.