A mean-field kinetic model was developed to describe a diffusion-controlled bulk cross-linking photopolymerization. This model incorporates all the physical transport limitations that directly or indirectly affect polymerization parameters and rate constants in such reactions. Events such as the continuous decrease in initiator efficiency and the presence of a temporary excess free volume were accounted for in the model development. Rate equations were written for each of the species present in the reacting system. The initiator efficiency was calculated throughout the reaction using a model previously developed by us. The propagation rate constant was calculated using the Smoluchowski rate expression and the Vrentas-Vrentas theory. Radical mobility caused by propagation diffusion was incorporated in the calculation of the termination rate constant. Where the values of model parameters were not available, typical values were calculated using predictive methods or group contribution methods. The model was able to predict kinetic results of diethylene glycol diacrylate photopolymerizations.