The temperature and pressure dependence of the thermal pressure coefficient and internal pressure for eight polymer solids are calculated. The principal results are as follows : (1) The pressure dependence of the thermal pressure coefficient at constant temperature is relatively small. (2) For some solid polymers, as a function of temperature, a maximum in the thermal pressure coefficient is predicted in the solid region, and the temperatures corresponding to the maximum values are estimated. (3) For most solid polymers, the zero-pressure internal pressure increases with increasing temperature over the entire temperature range to the glass transition temperature or the melting point.