Objectives: To evaluate the contribution of community-based respiratory virus infections to lower respiratory tract disease in HIV-1 infected individuals. Design: Prospective clinical cohort study. Setting: Specialist in-patient unit for HIV and AIDS, University College London Hospitals, London. Subjects: 44 consecutive HIV-1 antibody positive patients who underwent 47 diagnostic bronchoscopies for evaluation of the symptoms and signs of lower respiratory tract disease. Time: Winter months of 1994/95. Main outcome measures: Detection, in bronchoscopic alveolar lavage fluid, of infection with influenza A and B, respiratory syncytial virus (RSV), parainfluenza 1, 2 and 3 (by immunofluorescence and cell culture) and adenovirus and enteroviruses (by cell culture). Results: No evidence of influenza, RSV, parainfluenza, adenovirus, or enterovirus infection was detected. Conclusions: Despite a marked increase in RSV and influenza B infection in the general population over the winter of 1994-95, respiratory virus infections were not detected in this cohort of HIV infected patients. As the organisms causing lower respiratory tract disease were related to immunosuppression, this study questions the value of routine identification of community-based respiratory viruses in this patient group.