Recent experimental observations of draining colloid-laden liquid films show stepwise film thinning, as opposed to continuous thinning that occurs in films without colloid particles. The steps are also shown to propagate at a rate that depends on the diameter of the film. In this project, a mathematical model of a thin liquid film containing colloidal particles is derived from the laws of fluid dynamics in a cylindrical coordinate system. The particles in the film give rise to an oscillatory component of the disjoining pressure that is absent in particle free films. Solutions of the model show that a uniform film is unstable to layering. The overall goal of the work is to predict the stepwise thinning behavior seen in experiments, and to understand the physical reasons behind this and other observed film behaviors.