Algorithms suitable for use on parallel computers are being developed to simulate the scattering and absorption of light by small penetrable objects such as ice crystals and biological cells. The solution of the problem is based on a geometrical optics approach. Each incident ray undergoes multiple reflections and refractions as it travels through the scattering object. Data parallel algorithms have been developed which assign one processor to each incident ray. A massively parallel architecture consisting of 64 K processors (the Connection Machine) is being used. This means that the scattering calculations for over 65000 rays can be carried out simultaneously. Using a stochastic approach, a Monte Carlo technique is used whereby each ray is either reflected or refracted based on probabilities.>