Occupational lung disease was studied in workers who mined and milled talc (14807966) in New York, Montana, Texas, and North Carolina. Occupational exposure to talc has been associated with silicosis and interstitial fibrosis. In the population studied, personal air samples were collected to determine time weighted average exposures to respirable dust, free silica, and mineral particulate. Cumulative exposures were calculated on the basis of job classification. Chest radiographs and pulmonary function tests were evaluated for all workers. The entire study population was classified according to age, height, sex, smoking habits, weight, region of employment, and presence or absence of cough, phlegm, dyspnea, and pleural thickening. Analysis of intraregion dose response relations showed no consistent or strong association of exposure with respiratory symptoms and pulmonary function. A statistically significant association of bilateral pleural thickening with exposure was found, and was dose related in all regions except Texas. Sex, age, height, and smoking were, in general, significant predictors of pulmonary function. The authors conclude that their findings support the hypothesis that talc is a causative agent of pleural thickening. However, they state, the relationship between pleural thickening and mortality is unknown.