To evaluate the usefulness of MR in the osteomyelitis, we reviewed MR examinations of 14 patients with pyogenic osteomyelitis of the long bone. All 14 patients were confirmed to have osteomyelitis either surgically (13/14) or by aspiration (1/14) MRI was performed with 0.5T(n=8) or 2.0T(n=6) SE technique, and GD-DTPA enhanced T1W1 was obtained in 10 examinations. Anatomic location of lesions were femur (8/14) tibia (5/14) and fibula (1/14) The marrow cavity and soft tissue were involved in 13/14, 12/14 respectively. The signals of both intraosseous and extraosseous infected area were iso to low signal intensity to muscles on T1W1 and high signal intensity on PDWI & T2WI. Rim or diffuse enhancement of the marrow cavity and soft tissue were seen in all(10/10) cases. Sequestra, periosteal reaction. and cortical defect were found in 12/14, 10/14, 9/14. MR provided more accurate and detailed anatomic information including extent of disease and possible activity than bone scintigraphy, CT, or conventional radiography. We conclude that MR might be the choice of modality in the diagnosis of osteomyelitis of the long bone.