The materials phenazine and perylene have been previously reported to exhibit polymorphic behavior. Experimental evidence suggests that both molecules can exist in at least two polymorphic forms. In the case of phenazine. only one polymorph has a fully described crystal structure. In the case of perylene, two polymorphs have a reported structure, from single-crystal studies; however, one structure solution is of poor quality. This paper reports the results of a molecular modeling study and postulates crystal structures for the two polymorphs which lack a reliable experimental determination. Systematic searches of potential packing arrangements were conducted in the reported cells for both the solved and unsolved polymorphs of phenazine and perylene. A recently validated search method (Hammond, R. B.; Roberts, K. J.; Docherty, R.; Edmondson, M. J. Phys. Chem. B 1997, 101, 6532) was employed to rank packing arrangements by considering nonbonded atom-atom distances in combination with calculated lattice energies. The molecular packing arrangements were compared and contrasted using the packing energy breakdown routines within the program HABIT95 (Clydesdale, G.; Roberts, K. J.; Docherty, R. Quantum Chemistry Program Exchange 1996, 16, 1).