The intramolecular energies of helical conformations of isotactic poly(methyl methacrylate) have been optimized with respect to all bond angles and torsion angles occurring in the helix residue. The lowest energy conformations, belonging to the all-trans class, closely approximate 10/1 helices. The helix pitch (21. 1 A) coincides with the repeat distance indicated by crystallographic studies. Both of the bond angles in the chain backbone are appreciably distorted relative to the tetrahedral value.