According to the general function of the upper limb the importance of the human elbow joint is discussed including phylogenetic aspects. The ontogenesis of this joint is analysed by serially sectioned human embryos of different stages. The important period is at the end of the second month, as the articular elements are formed at this time. The density distribution of the subchondral bone of the elbow joint corresponds to the results from photoelastic models. They are compared with the stress diagrams calculated by Pauwels. The density distribution of the articulating elements corresponds to the local stress. The analysis of the elbow joint of children of different ages shows, that there is no basis connection between the shape of the different formed articular surfaces of the ulna and the orientation of the epiphyseal plate. For the structural changes of the articular surfaces in the incisura trochlearis ulnae functional explanations are given with regard to Pauwels' deductions on the mechanical stress and the hypothesis on the causal histogenesis.