Biodegradable composites of poly(propylene carbonate) (PPC) reinforced with unmodified cornstarch were compotmded in a batch mixer followed by compression molding. the effects of reinforcement on the morphology, static and dynamic mechanical properties, as well as thermal properties of PPC/starch composites, were investigated. Tensile tests showed that incorporation of starch improves the stiffness and tensile strength of composites significantly. Scanning electron microscopic examination revealed the existence of good interfacial adhesion between the fillers and PPC matrix. Moreover, experimental results indicated that the starch addition leads to a significant improvement in the thermal stability of the composites. This paper demonstrates that the incorporation of low-cost and biodegradable cornstarch into PPC provided a practical way to produce completely biodegradable and cost-competitive composites with good mechanical properties. (C) 2004 Society of Plastics Engineers.