Self-consistent-field molecular orbital theory has been applied to the hypervalent molecules hexamethylsulfur and hexamethylselenium. Using a double-ζ basis set augmented by d-like polarization functions on the central atom, one minimum of D3 symmetry is predicted for each compound. It is noted that these minima are only slightly distorted from octahedral ligand coordination. Molecular geometries, vibrational frequencies, and infrared intensities are predicted. Comparisons are made between these predictions and the predictions from the same level of theory applied to the dimethylchalcogens. The results of a preliminary investigation of hexamethyltellurium are also included. © 1993, American Chemical Society. All rights reserved.