Abstract : Mathematical models were developed to predict deposition of inhaled particles in the lungs of two strains of mice. The deposition model included an algorithm to calculate particle inhalability. Model predictions included filtering capabilities in the nasal passages, and deposition in various regions of the lung. Particle inhalability was smallest in mice compared with that for larger rodents and humans. In addition, there was a significant deposition of particles in the nasal passages, with the consequence of limited penetration of particles into the lung. As a result, particle deposition in lung airways was small, particularly for larger particles. The findings from the study indicated that mice inhalation studies should be conducted with sub-micrometer particles to allow for sufficient deposition in the lung to produce the desired biological responses.