Four beagle dogs were exposed by inhalation to polydisperse fused aluminosilicate particles labeled with 147Pm and 169Yb. The left or right lung of each dog was lavaged one or five times with normal saline to remove a portion of the particles. Autoradiographic and computer techniques were combined to determine the dispersion pattern of radioactive particles still in the lung after lavage treatment. For all four dogs the dispersion pattern of particles in the lung was similar for the lavaged and nonlavaged lung lobes. Examination of the autoradiograms indicated that lavage procedures did not preferentially remove particles from some area of the lung. The similarity of particle dispersion patterns suggests that minimal relocation of particles in lung results from lavage treatment.