The concentration and size distribution of bronchoalveolar lavage (BAL) asbestos fibers (AF) longer than 2 microns was determined by analytical transmission electron microscopy (TEM). The concentration of asbestos bodies (AB) was measured by TEM and light microscopy (LM). The study group consisted of 110 patients. 27 patients had no occupational asbestos exposure, 44 patients had occupational exposure to asbestos but no asbestos related disease and 39 patients had asbestos related diseases, either asbestosis (n = 34) or malignant mesothelioma of the pleura (n = 5) following long time asbestos exposure at the working place. Occupational asbestos exposure was reflected by increased asbestos fiber concentration in the BAL samples. Mean fiber concentration and size was different between the groups, but the scatter was large.