Corn starch was modified by addn. of ground bark (up to 30% by mass), and glycerol (20% by mass), and processed by extrusion at 80-120 degrees C and screw speed 60-100 rpm. The thermoplastic starch (TPS) granulates were studied for expansion index, microstructure and some mech. properties. The addn. of bark resulted in increasing homogeneity of the TPS structure and its elasticity. Unfortunately, insufficient binding of bark with starch matrix resulted in decreasing the compression strength of TPS. The addn. of 20% bark was found optimum amt. in the prodn. of TPS.