Intrapulmonary deposition of 1-mum-diameter particles of dioctyl sebacate was studied in 58 working coalminers. Total deposition was found to be significantly correlated with lung function measurements characterizing airway obstruction. The closest relationship was between deposition and the mean maximal flow rate in the third quarter of a forced expiration. The shape of the exhaled aerosol recovery curve was also found to be related to the degree of airway obstruction; 3 basic types are described. The concave type was more common in smokers, in whom deposition was significantly greater. The presence of simple pneumoconiosis was not associated with the degree of aerosol deposition. The significance of the findings of aerosol deposition and its recovery pattern are discussed in relation to the pathogenesis of lung disease.