The solid-state characterization of highly stereoregular poly(vinyl chloride) (PVC) prepared by urea clathrate polymerization was carried out by using various instrumental analyses. The structural differences of PVC appeared most remarkably in solubility to organic solvents, IR, WAXD, and solid-state C-13-NMR spectra. The value of the glass transition temperature (T-g) was about 90 degrees C, not as high as expected, although its detection was quite difficult. The thermal stability was poor, as evidenced by the easy discoloration of this polymer by heat treatment, which was related to the absence of a termination reaction. Dynamic ESR spectra in the solid state clearly indicate that the radical formation occurs at such a low temperature as 160 degrees C in the initial degradation stage. The degradation characteristics of urea clathrate PVC were critically discussed.