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This paper deals with the problem of the critical plane determination formultiaxial fatigue failure criteria. Experimental results from multiaxial proportional,non-proportional cyclic loading and variable-amplitude bending and torsion were usedto determine the macroscopic fracture plane orientations and the fatigue lives. Someknown multiaxial critical plane criteria were verified based on the fracture planeorientations and experimental fatigue lives. It was concluded that frequently the criticaland fracture plane orientations do not coincide. However, the morphology of fractureplanes is a key for an appropriate choice of the fatigue failure criterion for the fatiguelife estimation.