[Abstract] Objective: To observe the clinical effect of the polylactic acid membrane in the prevention of epidural scar adhesion. Methods: From July 1998 to April 2000, 62 inpatients with lumbar dics herniation were randomly assigned into two groups: an experimental group with 32 patients and a control group with 30 patients. All patients were treated with surgical fenestration, laminectomy and lumbar discectomy. Patients in the experimental group were implanted with a 0.1 mm polylactic acid membrane covering the interlaminar space. Patients in the control group were not implanted with any acid membrane to cover the interlaminar space. Two weeks after the surgery, the patients were examined for symptoms of local and systemic negative reactions. Six months after the surgery, the patients were reevaluated for any clinical symptoms and CT scans were employed to examine the epidural scars. Results: Two weeks after the surgery, neither the experimental group nor the control group showed any local or systemic adverse reactions. Body temperatures were within normal range. Wounds healed in Phase I. No abnormalities were detected during hepatic and renal function or blood routine examinations. Six months after the surgery, the curative effects of the experimental group and the control group were as follows: excellent in 27 and 24 patients, good in 4 and 4 patients, fair in 1 and 1 patients, and poor in 0 and 1 patients, respectively. There was no significant statistical difference between the two groups (P>0.05). The CT scans showed no adhesion between the epidural scar and the dural sac in all patients from the experimental group, while various degrees of adhesion were found in the patients from the control group. Conclusion: The polylactic acid membrane effectively prevented epidural scar adhesion with good biocompatibility without toxity. The value of its clinical application is promising.