Preexisting lung disease was examined as a risk factor for lung cancer in a population-based, case-control study of nonsmoking women in Missouri conducted between June 1, 1986, and April 1, 1991. A history of lung disease was reported by approximately 41% of 618 cases and 35% of 1,402 controls (odds ratio (OR) = 1.2; 95% confidence interval (Cl) 1.0-1.5. The risk was more pronounced when next-of-kin interviews were excluded (OR = 1.5). Previous lung disease was significantly related both to adenocarcinoma (OR = 1.4), which accounted for 62% of the cancers, and to all other cell types of lung cancer combined (OR = 1.8). Despite having discontinued smoking for more than 15 years, long-term ex-smokers were at a 2.2-fold risk of lung cancer compared with lifetime nonsmokers. Among lifetime nonsmokers, significant risks were noted for asthma (OR = 2.7) and pneumonia (OR = 1.5). Emphysema (OR = 2.6) and tuberculosis (OR = 2.0) were also significantly related to lung cancer, but only among former smokers. Chronic bronchitis was linked to elevated risks of nonadenocarcinomas only (OR = 2.3). Pleurisy was not reported more frequently by cases than by controls. Approximately 16% of all lung cancers among nonsmoking women could be attributed to previous lung diseases, most notably asthma, pneumonia, emphysema, and tuberculosis.