The structure of hexamethyltungsten, W(CH3)(6), was determined by x-ray single-crystal diffraction at -163 degrees C. The molecule has a strongly distorted trigonal prismatic structure with C-3v symmetry. This irregular structure is not a result of intermolecular forces, but rather represents its true molecular structure. A similar structure, which deviates less from the ideal trigonal prismatic structure, was determined for hexamethylrhenium, Re(CH3)(6). Although these structures violate the simplistic models used to predict the geometry of molecules, they are at least in part explainable by the molecular orbital model.