The Monte Carlo method was used to analyze characteristics of light scattering and absorption by living bodies. The intensity of transmitted light through a slab of emulsion which simulates living bodies was calculated. The emulsion contained two types of particles ; small particles with isotropic scattering and large particles with strong forward scattering. Time-resolved analysis clarified the profile of transmitted light intensity, and the optical density, which is calculated from light attenuation caused by absorbing particles, was found to be in proportion to the absorption coefficient of particles and the optical path length. From spatial analysis of transmitted light intensity, the mean optical pathlengths have been found to be four to ten times the geometrical pathlength.