Films of aliphatic polycarbonates prepared from epoxides and carbon dioxide were found for the first time to be degradable with a single enzyme, Rhizopus delemar lipase, at 37 degrees C in an acetate buffer solution. In the degradation of polycarbonates containing oxyethylene units, ethylene glycol could be detected in the buffer solution, and was quantified by GLC after conversion to its diacetate. The weight loss values after 168 h were in close agreement with those calculated from the yields of ethylene glycol. Under the same conditions the polycarbonates were degraded much more reluctantly than poly(butylene succinate), an aliphatic polyester. Rhizopus arrhizus lipase was not effective for the degradation of any of these polymers.