In operating conditions a component underlies a multiaxial stress condition. The reasons therefore are combined loadings and complex component geometry. The influence on the fatigue life of a component and the fatigue behavior of materials is subject of actual research projects. The first part of the diploma thesis deals with the systematic classification of multiaxial combined loadings and the definition of some main influences on the fatigue behavior. These main influences are load type, phase shift, frequency ratio, mean stresses and specimen geometry. Out of this, a testing program for collecting material properties of two selected materials is created. These materials are Austempered Ductile Iron (ADI) and Maraging steel. The results of the fatigue tests show partially high effects on fatigue behavior. An increasing frequency ratio is reducing the fatigue life, however, in contrast to this a phase shift is increasing the fatigue life of both materials. The effect of mean stresses and specimen geometry on the fatigue life is compared to uniaxial loadings. The strength hypothesis according to Gough describes the influence of the load type acceptable. Based on the results the fatigue behavior of Austempered Ductile Iron is opposed to the fatigue behavior of Maraging steel, in which the mechanical properties are compared. The second part of the diploma thesis deals with strength hypotheses and their capability to describe the fatigue behavior of material. The strength hypotheses are analyzed and compared with the fatigue strengths from the fatigue tests. The best results for both materials show the strength hypotheses according to Spagnoli, Liu/Zenner and Fröschl.