Conformations of adjacent reentry folds of polyethylene have been examined using molecular mechanics techniques. In addition to the lowest energy conformation (g(-)g(-)g(+)g(+)tg(+)) described in previous studies, other conformations with similar energies but different spatial extents were identified. In particular, a fold conformation was found which was less than 1 kcal/mol higher in energy than the global minimum (g(+)g(+)tg(+)g(+)tg(+)). The effects of different fold conformations on fold surface packing and the lamellar structure of polyethylene crystals were discussed. Fold energies for the five lowest conformations ranged from 4.5 to 6.2 kcal/mol. The small energy differences between the global minimum and the other conformations indicate that more than one fold type may be present in polyethylene crystals and should be considered in fold packing simulations.