The prevalence of chronic obstructive pulmonary disease was evaluated in 12,980 lifelong nonsmoking adults who participated in one of three National US Health and Nutrition Examination Surveys. Also evaluated were the relationships between chronic obstructive pulmonary disease and age, sex, ethnicity, education, income, and certain environmental and occupational factors. Overall, 4% of men and 5% of women reported physician-diagnosed chronic obstructive pulmonary disease. Prevalence increased with age and with decreasing household income, was higher in Whites than in non-Whites, and was particularly high in Hispanic women. Further research is needed to explain the excess risk for chronic obstructive pulmonary disease in economically disadvantaged nonsmokers, and to assess the role of environmental tobacco smoke in nonsmokers' risk for the disease.