The crystal energy of benzene was minimized with no constraints other than the existence of a lattice, starting from 60 structures with Pbca symmetry. The initial lengths of the sides of the unit cell were varied from one start to another. Ten distinct energy-minimized ordered structures were obtained; four of these structures had orthorhombic space group symmetries, five had monoclinic symmetries, and one was tetragonal. The energies of nine of the structures fell within a range of 1.0 kcal/mol; the energy of the 10th structure was 0.8 kcal/mol higher. One of the orthorhombic structures could be identified with the low-pressure orthorhombic crystal form of benzene, and one of the monoclinic structures could be identified with the high-pressure monoclinic form. With the empirical potential used for these energy minimizations, two of the monoclinic structures had lower energies than the orthorhombic structures. However, when energy minimization was carried out with two other potential energy functions taken from the literature, with or without an added term to reflect the effect of pressure, the relative energies of the orthorhombic and monoclinic structures favored the observed crystal structures at both low and high pressure. Comparison of the possible crystal structures of benzene found in this study with those found by Dzyabchenko (Dzyabchenko, A. V. J. Struct. Chem. 1984, 25, 416) showed that four were the same but the other six were new.