Laboratory animals are used as surrogates in inhalation exposure studies for (1) risk assessments of air pollutants and (2) evaluations of pharmacologic drugs. Herein, a mathematical model is presented that identifies factors affecting the regional distributions of inhaled aerosols within the complete respiratory system of the guinea pig. The model couples empirical and deterministic techniques. An original empirical formula is presented to describe particle losses in airways of the head and throat. Regarding the lung, its structure is defined using the asymmetric morphology of Schreider and Hutchens (1980), and deposition is calculated in a deterministic manner using the protocol of Martonen et al. (1992a, 1992b). Results of our deposition model are compared separately with the theory of Schreider and Hutchens (1979) and the experimental data of Raabe et al. (1988). Results of the deposition model presented herein are in qualitative agreement with the laboratory data of Raabe et al. (1988). Quantitative differences in desposition values may be attributable to different strains of guinea pig being used in the repective morphological and deposition studies. By identifying the factors that most affect the behavior of inhaled particles, our deposition model can aid in the design of inhalation exposure experiments and interpretation of data.