Multiaxial fatigue loading conditions are a key issue in several mechanical components. Studying the life of components subject to cyclic stresses is of utmost importance to avoid the unexpected failure of equipment, vehicles or structures. Among other parameters a correct definition of a fatigue cycle in multiaxial fatigue conditions appears crucial concerning the fatigue life issue. The objective of this work is an attempt to achieve a correct definition for a fatigue cycle in multiaxial loading conditions. A low alloy steel 42CrMo4 heat treated, quenched and tempered (500ºC) was used in this study. Based on achieved results a definition for a fatigue cycle in multiaxial fatigue loading conditions is proposed and some remarks are drawn.