The physical structure of poly(methylphenyl)silane (PMPS) has been investigated using wide-angle x-ray scattering at various temperatures and optical polarizing microscopy. The results obtained by these techniques clearly show the existence of an ordered phase in PMPS. The crystallinity of our sample was estimated to be about 10% at room temperature. Below 190 degrees C, the atactic chains pack into a monoclinic crystalline lattice of near hexagonal symmetry, with two types of disorder existing in the packing. At about 190 degrees C, a phase transition to a liquid crystalline columnar hexagonal packing (D-ho) occurs. Finally, the sample melts into an isotropic amorphous phase.