Pulmonary asbestos burdens are usually determined by quantitative pulmonary dust analysis. The aim of this study was to investigate the value of bronchoalveolar lavage (BAL) for this purpose. First, the upper limit of normal for asbestos bodies (AB) in BAL fluid was established using a reference group of 371 patients with no evidence of increased exposure to asbestos. 99% of these patients had less than 0.5 AB/ml. In order to see whether BAL fluid AB concentration reflected pulmonary tissue content, BAL fluid and lung tissue from a further 64 patients with diverse histories of asbestos exposure were investigated. There was a positive association between AB concentration in BAL fluid and lung tissue only for the overall group of 64 patients (r = 0.86; P < 0.001). Twelve of 13 patients with more than 1 AB/ml and ten patients with more than 5 AB/ml had more than 1000 AB/cm3 lung tissue, a value that is usually exceeded in asbestosis. When the upper concentration limit was set at 0.5 AB/ml for BAL fluid and 50 AB/cm3 for lung tissue, only two out of 64 patients had a false positive value (specificity 95%), but eleven patients had false negative results (sensitivity 58%). These investigations establish that concentrations of > or = 0.5 AB/ml are a reliable indicator of increased asbestos exposure and concentrations > 1 AB/ml are associated with a higher probability of having more than 1000 AB/cm3 lung tissue. However, exclusion of increased asbestos exposure is not possible on the basis of negative BAL findings, since the sensitivity of the method is too low.