Molecular mechanics force fields developed to model carbohydrate behavior in solution are commonly used to model the solid state behavior of cellulose. Simulation studies of cellulose fibrils with a variety of force fields have been reported, but it is difficult to compare results between different model systems, and a systematic study is warranted to determine which carbohydrate force fields are appropriate for further computational studies of protein-cellulose interaction. Significant variation in reported experimental observations of cellulose structure complicates the interpretation of structural changes that occur in simulated cellulose fibrils with different force fields, and these differences in structure may be due to simulation artifacts or may correspond to real metastable states of cellulose packing. Simulations of cellulose fibrils with several modern carbohydrate force fields will be presented, with a comparison to a variety of experimental observations.