The study presents clinical and diagnostic problems in patients with malignant bone metaplasia. Material is composed of 13 patients treated surgically between april 2002 and august 2007. In three cases tumors were localised in tibia, in 5 patients around distal femur, in 2 in pelvis, in 2 in humerus and in 1 in lumbar spine. None of the patients has had recurrence by february 2006 r, 12 patients have been free of the disease so far. However, one individual diagnosed with giant cell tumor metaplasia to osteosarcoma did not accept proposed therapy. The authors have particularly emphasized thorough clinical and radiological evaluation and the need of team work before surgical procedure.