To obtain valid information on stress tolerance of pertrochanteric fractures, we exposed three different methods of osteosyntheses to dynamical stress and the results were compared. The methods of osteosyntheses were application of a 130 degrees angle plate, performing an adjoining osteosynthesis with bone cement or using cephalocondylar nails. The measurements in connection with photographical and roentgenological examinations of osteosyntheses under stress gave the following results: Compared with the other methods treatment with condylar nails gave equal results in static behaviour yet was clearly superior in its dynamic reaction.