A series of fluorine-containing aromatic homopolyacetals and copolyacetals with a wide range of unit ratios were synthesized by the solution polycondensation of 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (bisphenol AF), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), or both with 2-(trifluoromethyl)benzal chloride, and the effect of fluorine substitution on the properties of these polymers is discussed in relation to the fluorine contents. High molecular weight polyacetals with reduced viscosities of 0.43- 0.97 dL/g were obtained in high yields with potassium hydroxide as a base, 18-crown 6-ether as a catalyst, and N-methyl-2-pyrrolidinone as a medium at 100 degrees C for 3 h. Regardless of the fluorine contents, these polymers all were highly soluble in various solvents, including benzene, chloroform, ethyl acetate, and tetrahydrofuran, and afforded colorless, transparent, and tough films by solution casting. The temperatures of 5% weight loss and 10% weight loss under nitrogen both increased significantly and monotonously with increasing fluorine content, whereas the glass-transition temperatures were scarcely affected by fluorine substitution. The dielectric constant at 1 MHz of the bisphenol AF-based homopolyacetal was 2.43, which was remarkably lower than the value of the bisphenol A-based homopolyacetal, 2.68.