A two year old boy was seen in the orthopedic clinics because of typical symptoms of Legg-Perthes disease, a scintigraphy with Technetium99m showed a distinct deficiency of nuclear activity in the femoral head which is characteristic of the early stage of Legg-Perthes disease. A routine blood count lead to the diagnosis of acute lymphoblastic leukemia. The boy was treated according to the Austrian cooperative leukemia protocol and complete remission was achieved. No orthopedic treatment of the femur head necrosis was done, after eight weeks of treatment with multiagent chemotherapy the boy started to walk again and subsequently became free of all symptoms of Legg-Perthes disease. A scintigraphy done eight weeks after the initial scintigraphy showed that the deficiency of radionuclear activity of the femoral head was nearly vanished. This case illustrates the variability of bone involvement in acute lymphoblastic leukemia, which often is the most prominent symptom at an early stage of the disease.