Objective : There were few reports about statistically significant factor which contribute to low back pain[LBP] after microscopic discectomy. We analyzed the result of percutaneous radiofrequency neurotomy[PRN] for low back pain after microscopic discectomy in lumbar disc herniation. Methods : Forty four patients with LBP after microscopic discectomy who were treated by one level microscopic discectomy from January 2003 to March 2004 were included in this study. They were divided into two groups by the presence of preoperative LBP into preoperative back pain group [group I] and postoperative back pain group [group II]. Radiofrequency procedures were performed in the usual manner, targetting the medial branch of L4, L5 and Sl. Pain relief was estimated at 1 week, 1 month and 6 months following the procedure, using the visual analogue scale. Above 50% pain relief was defined as the positive response. Results : Positive responders were 16 patients [73%] at 1 week, 12 patients [55%] at 1 month, and 7 patients [32%] at 6 months after PRN in group I. In Group II, 18 patients, 15 patients and 13 patients responded positively after 1 week, 1 month and 6 months after PRN, respectively. Conclusion : PRN is an effective treatment for newly developed low back pain after microscopic discectomy. There was no morbidity in our series, but long-term follow up is necessary.