Objective To explore the differences between transient osteoporosis of the hi p (TOH) and bone marrow edema (BME) associated with osteonecrosis of the femoral head (ONFH) in terms of cl inical practice and imaging. Methods From January 2006 to February 2008, 5 hips of TOH in 5 cases (1 male and 4 females, aged 29-42 years) and 67 hips of BME associated with ONFH in 63 cases (53 males and 10 females, aged 18-70 years) were analyzed. According to ARCO classification, there were 23 hi ps of stage II, 43 hi ps of stage III, and 1 hi p of stage IV. The induced factors, the degree of pain, the duration of pain and commemorative symptoms were compared. The X-ray, MRI and ECT were also compared. Results There were no differences in induced factors, the degree of pain, joint effusion and ECT between TOH and BME associated with ONFH. TOH had no risk factors, antecedent symptoms and commemorative pain. There were 2 hips with TOH which showed osteopenia on X-ray films. The location of edema was in the superior part or the whole femoral head.A total of 65 hips with BME associated with ONFH had related causes of disease, 10 had antecedent pain and 59 had change of hardening on X-ray films. The X-ray films showed sclerotic area and the edema changes on MRI surrounded the necrotic lesion. The pain just amel iorated when BME disappeared. Conclusion There are differences between TOH and BME associated with ONFH on symptoms, X-ray films and MRI.