Studies on the possibility of the application of the solid-state postpolycondensation (SSP) process to increase the average molecular weight of bisphenol A-based polycarbonate (PBC) were carried out. The thermally stable PBC with a very high molecular weight reaching about 50,000 g/mol was obtained by the applied SSP technique. Some factors influencing the effectiveness of the SSP process were initially examined: the mode of preparation (crystallization) of the PBC prepolymer, condensation temperature and time, and the vacuum applied in the reaction vessel. It was found that the superior yield of the high molecular weight PBC was obtained by the employing as high as possible values of the parameters taken into consideration.