The relative usefulness of various initial findings in predicting survival is reported for 200 patients with chronic obstructive pulmonary disease who have been followed for approximately 15 years. After 5 years of follow-up, subjects 62 or more years of age showed a poorer survival rate than younger subjects. After controlling for age, the per cent predicted forced expiratory volume in 1 sec after administration of bronchodilator was the best indicator of prognosis. In subjects less than 65 years of age, the presence or absence of cor pulmonale further improved the prediction of subsequent mortality. Regardless of initial findings, however, there was wide individual variability in prognosis, and factors relating to this variability remain obscure. No difference in survival rate was noted between the 178 male patients who were enrolled in Chicago 15 years ago and the 100 similarly impaired men enrolled in Tucson approximately 7 years ago.