A statistical approach is still the most effective tool for handling coupled absorbing and scattering phenomena in a heterogeneous system for the assessment of light energy absorption in a photoreactor. A Monte Carlo simulation model has been developed for the prediction of light intensity distribution in a photoreactor. The model has three parameters, an attenuation coefficient, a probability of light ray absorption, and a scattering parameter which specifies the mode of isotropic and/or anisotropic scattering, Experimental measurements of light transmittance and reflectance through solid particle suspensions hounded by two infinite plates were carried out using a newly designed integrating sphere device attached to a spectrophotometer. Light intensity distributions in a rectangular photoreactor with the suspension irradiated hy a laser beam were also measured with a photo-probe, These data are compared with simulation results and model parameters are determined to satisfy the experiments, Light absorption fractions measured in the suspensions with different optical lengths show satisfactory agreement with those estimated by the simulation, Thus, the model developed is verified to he effective for the assessment of light absorption rates in a heterogeneous photoreactor.