To determine whether chronic lower respiratory tract disorders contributed to the development of chronic mountain sickness (CMS), we compared hemoglobin (Hb), oxygen saturation (SaO2), peak expiratory flow rate (PEFR), and CMS scores (CMSsco) in 97 normal men at high altitude with those of men at high altitude with acute (ARD; n = 12), chronic upper (CURD; n = 33), and chronic lower (CLRD; n = 34) respiratory diseases. The clinical diagnosis of the different types of respiratory disorders was based on the results of a questionnaire and physical examination performed during an epidemiologic study. The CLRD group had higher CMSsco and Hb concentrations, and lower SaO2 and PEFR values when compared with the other groups. The frequency of low PEFR and SaO2 and high Hb and CMSsco was substantially higher in men with CLRD when compared with normal subjects. The results support the hypothesis that there is an association between signs and symptoms of CMS, as measured by the CMSsco, and CLRD. The chronic hypoxemia, product of chronic lung diseases, would cause excessive erythrocytosis and increase the signs and symptoms of CMS. Studies of Hb, PEFR, pulse oximetry, and CMSsco are recommended for early detection of high-altitude natives at risk of developing CMS.