Novel regular network polyesters were prepared from pentaerythritol (Xp) and aliphatic dicarboxylic acids of different numbers of methylene groups (HOOC(CH2)(n)-2COOH, n = 4, 6, 8, 9, 10, 12, 14, 16, and 20). Prepolymer prepared by melt polycondensation was cast from dimethylformamide solution and postpolymerized at 270 degrees C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, nide angle X-ray diffraction analysis, density, thermomechanical analysis, differential scanning calorimetry, tensile test, water absorption, and alkali hydrolysis. The enzymatic degradation estimated by weight loss of the network polyester films in a buffer solution of various kinds of lipases at 37 degrees C was studied. The enzymatic degradation of Xpn films was compared with that of the network polyester films of glycerol with various aliphatic dicarboxylic acids reported earlier.(12) After a 6 day incubation in Rhizopus delemar lipase solution, the weight loss was hardly observed for Xp4-8, while it increased gradually for Xp9-14 and showed the maximum weight loss of 13 g/m(2) for Xp14; then the weight loss decreased abruptly for Xp16-20. Other lipases of porcine pancreas and Candida rugosa hardly degraded Xpn films.