The past decade has witnessed a growing appreciation of the existence, frequency, and potential lethality of community respiratory virus infections such as RSV in some subsets of immunocompromised adults. The enigmatic "idiopathic pneumonia" and "pneumonia of unknown origin" have become more fathomable. As a result, a simple upper respiratory illness in a high-risk immunocompromised adult is no longer viewed as trivial. The paramount importance of simple hygienic practices has been underscored, and contamination of high-risk immunocompromised patients with respiratory secretions is now discouraged with the same rigor as contamination with urine, feces, or blood. Likewise, the risks and benefits of administering intensive chemotherapy in the setting of a seemingly benign upper respiratory illness are now weighed heavily. The diagnosis is suspected and pursued, and the available therapies are administered promptly. Widespread efforts are now under way to elucidate the pathogenesis of these viral pneumonias and to identify the immunodeficiencies predisposing patients to serious disease. In addition, efforts are being made to develop effective diagnostic, prophylactic, and therapeutic strategies. The growing need for more effective, easier-to-administer, less costly antiviral therapy is apparent.