Parametrical elastic-plastic finite element analyses of a circumferentially notched shaft subjected to multiaxial synchronous fatigue loading are performed considering two load combinations: (1) constant tension with cyclic torsion and (2) constant torsion with cyclic tensioncompression. The load amplitudes and the mean loads are varied to investigate their influences on the local stress-strain responses. The Multilayer Plasticity Model of Besseling in conjunction with the von Mises yield criterion is applied to describe the elastic-plastic material behavior. Coarse and fine meshes as well as three different types of multilinear approximations (twenty-, five- and threesegments) of the material stress-strain curve are used. Numerical results are presented to reveal the mutual interactions between the applied normal and torsional loads and the stress-strain response at the notch-root.