A primary malignant bone disease can generally be suspected on the basis of x-ray findings and may be even highly probable if several signs of malignancy are seen on one and the same film. Such changes include bone lesions larger than 6 cm on the first film with blurred outlines, showing patterns of destruction resembling moth-eaten textiles, the covering periosteum revealing spicula or Codman's triangles. Rapidly growing tumours can break cortex components from the continuous layer and shift them outwards. Roentgenological case controls are useless and must be replaced by a sample excision, since x-ray malignancy signs have no absolute value as decisive criteria in view of the fact that they are seen, inter alia, also in osteomyelitis, myositis ossificans and callus formations.