A secondarilly remodelled bone (the haversian bone) forming a wall of human shaft represents a significantly anisotropic material, which has different strengths in different directions. One of the factors influencing mechanical properties (strength in particular) of the bone is the architectonics of the compact bone. Osteons of the haversian bone are arranged in the direction of the dominant first principal stress and create two antirotational spiral systems in the opposite walls of the shaft. The aim of the work was to found out how the bone tensile strength depends on the orientation of osteons and check whether the premise applies that the architectonics of the haversian bone depends on the directions of the first principal stress and in what relation of strength moments the direction of the first principal stress corresponds to the actual orientation of osteons. The results of the tensile strength tests in wet samples from 10 femurs and the strength of the whole shaft in 9 pairs of femurs (cadaver material) have confirmed the premise that osteons are arranged in the directions of the dominant first principal stress and depend on the relation between bending and torsion moments. The strength of the femoral shaft is maximal in the physiological way of loading, i.e. in medial bending and outer rotation. The decisive motion on which the strength of the bone depends is torsion. In non-physiological loading the femoral shaft (by an opposite bending moment or opposite torsion moment in medial bending) the strength of the bone is significantly lower. From the biomechanical viewpoint the architecture of the haversian bone has an optimal and efficient structure. Key words: compact bone, bone strength, types of loading.