To investigate the pathogenesis of lower respiratory tract symptoms during rhinovirus infection, 19 healthy young adult volunteers were exposed to a currently unnumbered rhinovirus strain (HH). Spirometry and bronchoprovocation with histamine sulfate were performed prior to and on Days 4, 5, and 21 after exposure to the virus. Fiberoptic bronchoscopy for visualization and culture of the tracheobronchial mucosa was done on Day 4 or Day 5. Fourteen of 19 volunteers were infected with rhinovirus; 9 of the 14 had clinical illness. Rhinovirus was isolated from the bronchial brush specimens in 5 of the 13 infected volunteers bronchoscoped, all of whom had clinical illness. Rhinovirus was not isolated at bronchoscopy from any of the 5 infected volunteers without clinical illness (p = 0.025, Fisher's exact test). Spirometry and histamine bronchoprovocation were unchanged during experimental rhinovirus infection. Rhinovirus may invade the lower respiratory tract in symptomatic infections, and thereby cause lower respiratory tract symptoms.