Existing methods for estimating lung burdens of radionuclides with low-energy γ or x-ray emissions have limitations in their accuracy and availability. In this study, we evaluated the utility of bronchoalveolar lavage and assay of radioactivity in recovered lavage fluid as a bioassay tool to estimate lung burdens of plutonium. Six adult beagles briefly inhaled a polydisperse aerosol of230PuO2, treated at 1150°C, to achieve individual lung burdens of about 200 nCi. On the sixth day after exposure, a portion of each lung lobe of each dog was lavaged with 50 ml of saline. The dogs were killed, and tissue samples were obtained for radiochemical analysis. Using the relationship between regional deposition patterns of aerosols and the measured recoveries of plutonium in each lavage sample, the lung burden of each dog was estimated. The mean ratio for the lung burden estimates using lavage samples compared with the radiochemically determined lung burden was 1.0±0.6. This precision was similar to that obtained from in vivo measurement of plutonium x-rays, a standard bioassay procedure for plutonium inhalation cases. This suggests that the bronchoalveolar lavage technique may have applicability in situations where in vivo x-ray measurement is not feasible, or where lung burden estimates in addition to those obtained from in vivo measurement are valuable. The technique may also have utility for assessing inhalation exposures to other relatively insoluble materials, including nonradioactive chemicals.