The monomers p-hydroxystyrene (p-HS) and p-methoxystyrene (p-MS) have been synthesized and polymerized using azobisisobutyronitrile as free-radical initiator. The polymerization behavior of p-HS is anomalous, and a mechanism is suggested to account for this phenomenon. Poly(p-hydroxystyrene) (PHS) and poly(p-methoxystyrene) (PMS) homopolymers have been subjected to vacuum pyrolysis at temperatures in the range of 300–500°C. The products of degradation have been identified and qualitatively and quantitatively analyzed and the degradation behavior of the two systems compared with polystyrene. PHS shows anomalous behavior resulting from the high reactivity of the p-HS monomer and the facility for transfer afforded by the proton of the hydroxyl substituent. Mechanisms to account for the degradation behavior of each system are discussed.