We experienced three cases of lower respiratory tract infections worsened after Rhinovirus infection. Case 1: A 42-year-old male with diffuse panbronchiolitis was admitted to our hospital with the complaint of dyspnea on November 21, 1988. Rhinovirus was isolated from nasal washing and P. aeruginosa was cultured from transtracheal aspiration (TTA). Case 2: A 67-year-old male, whose underlying disease was pulmonary asbestosis, was admitted to our hospital complaining of pyrexia on June 12, 1990. Rhinovirus was isolated from TTA and H. influenzae and others were cultured from TTA. Case 3: A 64-year-old male with pulmonary emphysema was admitted to our hospital with a complaint of dyspnea on August 11, 1989. On December 17, 1989 the patient developed rhinorrhea and complained of purulent sputum, pyrexia and dyspnea after five days. Rhinovirus was isolated from nasal washing and TTA and S. nonhaemolyticus and others were cultured from TTA. As indicated in this report, it is interesting to study the relationship between viral infection of the upper respiratory tract and bacterial infection of the lower respiratory tract.