Objective To investigate the use of sodium hyaluronate and the preservation of epidural fat in the prevention of epidural scar adhesion after microendoscopic discectomy (MED). Methods A total of 300 patients receiving MED from July 2000 to October 2001 were randomly divided into 2 groups: patients in group A were given sodium hyaluronate with the preservation of epidural fat, while those in group B were on the contrary. Results The mean follow-up duration was 42 months in the group A and 44 months in the group B, respectively. The rate of excellent or good results was 98.6% in the group A (144/146), while 93.8% in the group B (135/144) ( ? 2=4.731, P =0.030). Postoperatively, the pain reappeared in 4 cases in the group A and in 6 cases in the group B, respectively, in which a re-operation was required. Re-operations found the epidural scar adhesion was grade 0 (3 cases) and grade 1 (1 case) in the group A, and grade 2 (2 cases) and grade 3 (4 cases) in the group B ( P =0.005). Conclusions Use of sodium hyaluronate with the preservation of epidural fat can improve the efficacy of MED and effectively prevent epidural scar adhesion.