Poly(epsilon-caprolactone) (PCL) of bimodal molecular weight distribution was exposed to the action of enzymes-lipases from Aspergillus oryzae in phosphate buffer at pH 7 and 37 degrees C, and those produced in situ by Bacillus subtilis in nutrient medium at 30 degrees C for 42 days. The occurrence of biodegradation is proved on the basis of the weight loss, decrease of molecular weight, carbonyl index, crystallinity, and development of cracks on the PCL surfaces. In the case of Bacillus subtilis, the degradation (10 wt % loss of PCL) proceeds faster in comparison with lipase from Aspergillus oryzae (2.6 wt % loss of PCL), where the degradation process seems to stop during 14 days of experiment. The gel permeation chromatography results reveal that preferential degradation of lower molecular portion did not occur but it is assumed that PCL chains were cleaved in accordance with particular degradation mechanism that depends significantly on biological agent. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013