In haematological systemic diseases such as acute and chronic leukoses, malignant lymphomas, lymphogranulomatoses, osteomyelofibroses, polycythaemias and aplastic anaemias with a different proportion changes of the bones in form of osteoporoses, osteolytic processes and deformations of the vertebral bodies are to be found. The proof may be performed radiologically and histologically. In 461 patients with different haematological diseases absorption measurings of monoenergetic rays of a J-125-source were performed at the distal third of radius and ulna. It was shown that the bone mineral content of patients with proved bone destructions did not significantly differ from the normal group. The too peripherally located place of the measuring and also the late inclusion of the compacta into the changes is regarded as cause for the negative result.