Surface treatments using glow discharge plasmas from O-2 and Ar were applied to blend sheets of poly(epsilon -caprolactone)-polycarbonate (PCL/PC), which had been produced by extrusion from melts of the mixture at various blend ratios. As to the reactivity of these two plasmas, O-2-plasma forms the oxidative species to be reactive in general, while Ar-plasma is non-oxidative. Weight loss by the oxidative O-2-plasma etching increased with the content of PCL in the polymer blends. The surface became hydrophilic by plasma treatment, and the changes were affected also by the blend ratio. PC and the PC-rich blend sheets became more hydrophilic than the PCL-rich blends after plasma treatments. The O-2-plasma treatments were more effective than non-oxidative Ar-plasma treatment in increasing the hydrophilicity. Hydrophilic change was related to the increase in the polar contribution of surface energy.