From the summary: Recently [the first author et al., ibid. 36, No. 23, 3497–3516 (1999; Zbl 0996.74071)], a method has been proposed for determining material true stress-strain curve with rectangular tensile bars up to localized necking. In the proposed method, material true stress-strain curve can be directly calculated from the load versus thickness reduction (at the minimum cross-section) curve. The method was established based on the finite element (FE) analysis for isotropic materials. In this study, this method has been extended for materials with isotropic elastic properties but anisotropic plastic properties. Two cases, transverse anisotropy and planar anisotropy, have been considered. Hill’s anisotropic material model implemented in ABAQUS is applied for the study. More than 30 three-dimensional FE analyses of rectangular specimens with different anisotropy values, hardening exponents and cross-section aspect ratios have been carried out. It is shown that the relation between thickness reduction and total area reduction of a given cross-section is influenced by material plastic anisotropy. It is, however, found that the anisotropic effect on the thickness-area reduction relation can be normalized by the width to thickness strain increment ratio, and a modified thickness-area reduction relation is proposed and verified numerically and experimentally.