39 patients with pathological fractures of the humerus were treated by isoelastic polyacetal endoprosthesis. Ten patients received a humeral-head-prosthesis and 32 a prosthesis of the humeral-shaft. The average survival time was nine months. Three times within the first group of twelve patients fracture of the cone of the prosthesis occurred. Therefore an additional stabilization of the contact zone between bone and prosthesis by plate-osteosynthesis was performed in the following 20 operations, preventing breakage of the material. In contrast to the conventional posterior approach to the humeral-shaft we chose a ventrolateral approach between the biceps and triceps muscle. This technique is less traumatic and leads to a shorter operation time. In patients with pathological humeral fractures a conception of treatment is demonstrated which provides an immediate stability by using endoprostheses to preserve the quality of life of oncological patients.