Objective To evaluate the prel iminary cl inical outcomes of percutaneous endoscopic lumbar discectomy (PELD) for patient with discogenic chronic low back pain (CLBP) and fail ing to respond to conservative treatment. Methods From June 2007 to May 2008, 52 patients with CLBP and fail ing to respond to conservative treatment were treated, including 15 males and 37 females aged 29-46 years old (average 38.2 years old). Those patients were diagnosed ith discogenic pain by low pressure discography. Duration of CLBP was 6-110 months with an average of 32.1 months. MRI exam revealed 108 “black intervertebral discs” low in signal on T2 image, including 3 discs of L2,3, 17 of L3,4, 48 of L4,5 and 40 of L5-S1. Pressure-controlled discography showed positive response, fluoroscopy or intraoperative CT confirmed annulus fibrosus tears of posterior intervertebral disc in 79 discs. PELD was performed. Visual analogue scale (VAS) was evaluated before operation, 1 month after operation and at the final follow-up. The cl inical outcome was determined by modified Macnab criteria at the final follow-up. Results The average operation time of each disc was 30.7 minutes (range 21-36 minutes), and the mean length of postoperative hospital stay was 3.7 days (range 2-5 days). No compl ications such as infection and the injury of blood vessels and nerves occurred. Transient paralysis of nerve occurred in 5 cases on operation day, and those symptoms were disappeared at the final follow-up visit without special treatment. Fifty-two cases were followed up for 3-15 months (average 7.3 months). VAS score before operation, 1 month after operation and at the final follow-up was (7.34 ± 1.52), (3.62 ± 0.92) and (1.57 ± 0.48) points, respectively, indicating there were significant differences compared with preoperative score (P lt; 0.01). According to the modified Macnab criteria, 11 cases were graded as excellent, 23 as good, 13 as fair, 5 as bad, and the excellent and good rate was 65.38%. Conclusion Prel iminary study suggests that PELD is safe and effective in treating patient with discogenic CLBP and fail ing to respond to conservative treatment.