Respiratory symptoms, radiographic findings, and lung function were analyzed in 144 Finnish patients with silicosis. The prevalence of persistent phlegm production in these patients was 46% and that of dyspnea 87%. Impairment of the vital capacity (VC) and the diffusion capacity (DLCO) (less than 80% of predicted values) were found in 46 and 47% of the patients with simple silicosis, respectively. The mean DLCO was lower in patients with advanced simple silicosis (category 3) than in those with slight simple silicosis (categories 1 and 2). In category 3 the DLCO was impaired in 9 out of 12 patients, the impairment being below 65% of the predicted values in six of the nine. All patients with large opacities showed impairment in their lung function tests. Twenty-eight of the silicosis patients had referents matched for exposure to silica dust, age, and gender. The referents had no radiographic signs of silicosis. The patients experienced dyspnea more often than their referents, whereas no difference was found in the prevalence of persistent phlegm production. The mean values of VC, forced expiratory volume in 1 s (FEV1.0), and DLCO were lower in the patients than in the referents. The results indicate a high prevalence of dyspnea, restrictive impairment of lung function, and impaired diffusion capacity in the patients with simple or complicated (ie, large radiographic opacities) silicosis. The DLCO proved to be a rather sensitive lung function parameter for advanced simple silicosis.