Abstract: Recent studies have shown that the size of microvoids has a significant effect on the void growth rate.The purpose of this paper is to explore whether the void size effect can influence plastic flow localization in ductile materials.We have used the extended Gurson's dilatational plasticity theory,which accounts for the void size effect,to study plastic flow localization in porous solids.The localization model of Rice is adopted,in which the material inside the band may display different response from that outside the band at the incipient moment of plastic flow localization.The present study shows that the void size has some effect on the uniaxial tensile curves,but little or essentially no effect on the shear band angle.