Objective: The purpose of the present study is to analyze the possible factors affecting the prognosis of osteonecrosis of the femoral head(ONFH), discuss the relationship between bone marrow edema(BME) and the instability of the femoral head, as well as the the consequent influences caused by the concurrent BME in the early stages of osteonecrosis.  Materials and Methods: We have adopted a case-controlled method to compare the differences of the final clinical outcomes. All the cases were come from the patients who were diagnosed nontraumatic ONFH with ARCO I or II stages in our center of hip diseases of the first affiliated hospital of Guangzhou university of TCM during January 1997 to April 2006. The cases are divided into two groups according to whether or not they had any BME phenomenon discovered by MRI. At last, 105 cases with 113 hips were taken into investigation, among which 53 cases with 58 hips were without BME while 52 cases with 55 hips were with it. Each group was matched based on the patients' age, gender, etiology, stage, and the size of the lesion. Statistic analysis suggests that there is no significant difference between the two groups (P>0. 05). Both of the two groups had been treated with "Shen Mai Chen Gu Troche" together with controlled weight-bearing rehabilitation. After an average of 27. 6 months' (3-66) follow up, the differences of prognosis between the two groups are observed. Evaluation criterions of the prognosis are mainly based on the radiographic progression and the collapse condition of the femoral head. We also set the occurrence of collapse as the survival outcome event, and use the Kaplan-Meier survival analysis. The two groups' prognosis are compared after having used the same intervened measures during a certain period of time. The results of research are processed by SPSS 11.0 software. The significance is set at P<0. 05 and the confidence intervals is 95%.   Results: In the Non-BME group, 26 hips developed radiographic progression after treatment in 58 hips, occupying 44.83%; while in the BME group, 41 hips developed radiographic progression after treatment in 55 hips, occupying 74. 55%, which is much faster than that of Non-BME group. The collapse rate after treatment in the BME group(54. 55%) is much higher than that of Non-BME group(17.24%, P<0.05). 65.75% of the Non-collapsed femoral heads had no BME before treatment; while 75% of the collapsed femoral head had BME before treatment, and the collapse rate is increased with the degree of BME. Collapse happened to all of those 13 patients whose BME degree were grade 3. The Kaplan-Meier survival analysis suggests that the survival rate in Non-BME group(82. 76%) is significantly higher than that of BME group(45. 45%, P<0. 05). It can be inferred that the prognosis of the early stages of osteonecrosis is relatively worse when it comes with BME.  Conclusion: 1. Mechanical stress factors impose great influence on the happening of BME. BME might be closely related to the instability state of the femoral head in the early stages of osteonecrosis. 2. BME is one of the most important factors that affecting the prognosis of ONFH. The prognosis in the early stages of ONFH is relatively worse when it comes with BME, which suggests that when BME is found in ONFH, some certain measures must be taken promptly in order to prevent it from getting worse.