Novel optically active biodegradable network polyesters were prepared from L- and D-malic acid (Ym(L) and Ym(D)) and glycols of different number of methylene groups (HO(CH2)(n)OH, nG, n = 2-6, 8-10. and 12). Prepolymers were prepared by a melt polycondensation, and the prepolymer films cast from dimethylformamide solution were postpolymerized at 220 degrees C for various periods of time to form network films. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by C-13 nuclear magnetic resonance, gel permeation chromatography, infrared absorption spectra, wide-angle X-ray diffraction analysis, density measurement, differential scanning calorimetry, thermomechanical analysis, and scanning electron micrographs. The biodegradation experiments for the network polyester films were carried out in enzymatic solution with Rhizopus delemar lipase and in an activated sludge. The degree and rate of biodegradation were estimated by the weight loss of the films. After the incubation for 10 days at 37 degrees C in Rh. delemar lipase buffer solution, the weight loss significantly depended on the number of methylene groups in the glycol component and showed the maximum weight loss of 52 g/m(2) for 4GYm(L) (6.8 g/m(2) in the absence of Rh. delemar lipase). In the exposure to activated sludge, the network polyester films showed a similar dependence of weight loss on the number of methylene groups as in the case of the enzymatic degradation, while the rate of biodegradation was much slower than that of the enzymatic degradation. The effect of stereochemistry of network polyesters prepared from L-/D-malic acid on the biodegradability was also investigated: the rate of the biodegradation for the network polyesters with L-isomers was slightly higher than that for those with D-isomers.