[en] Inhalation exposures of 30 Beagle dogs were conducted using monodisperse and polydisperse aerosols of ²³⁸PuO₂ to measure the initial pulmonary deposition and short term translocation of ²³⁸Pu to other tissue. Three sizes of monodisperse aerosols (0.7, 1.5, 3.0 μm AD) were compared with a single polydisperse size (1.5 μm AMAD) in this study. Animals were sacrificed at 0, 8, and 32 days after inhalation exposure and tissues analyzed for ²³⁸Pu content radiochemically. Initial pulmonary deposition decreased as monodisperse particle size increased and the polydisperse aerosol closely resembled the smaller monodisperse size in initial deposition. Upper respiratory clearance was nearly complete at 8 days after inhalation. Minimal translocation of ²³⁸Pu to tissues was found at 8 and 32 days post-inhalation exposure. Transport of ²³⁸PuO₂ particles to tracheobronchial lymph nodes appeared to be particle size dependent at 32 days after inhalation. (U.S.)