The effect of high-boiling solvents (N-acetylpiperidine, N-benzoylpiperidine, and N,N-dimethylbenzamide), temperature (185-260°C), and polycondensation time (2-30 h) on the reduced viscosity of the forming poly(arylene ether ketones) is studied for the interaction of 4,4-difluoro- and 4,4'-dichlorobenzophenones with bisphenol A, phenolphthalein, and phenolfluorene. It is shown that polymers of the highest molecular mass (reduced viscosity up to 1.08 dl/g) are synthesized in N,N-dimethylbenzamide at 240°C and those of the lowest molecular mass (reduced viscosity 0.26 dl/g) are synthesized in N-acetylpiperidine at 185°C.