Analgesic efficacy and analgesic duration of radiofrequency lesion treament of the facet rhyzotomy were investigated in 61 patients in a randomized prospective study. Before treatment, the putative pain-provoking vertebral facet was identified by diagnostic blocks with a local anesthetic agent, and 124 cases were divided into 2 groups randomly. The low temperature group (n=62, group 1) was treated with a radiofrequency lesion of 45-50°C and in the high temperature group (n=62, group 2) a temperature of 60-65°C was applied. We assessed monthly the analgesic efficacy of the facet rhyzotomy for 12 months. The analgesic effect of the treatment in both groups was identical. The mean analgesic duration±SD was 6.7±4.0 months in group 1 and 7.1±3.6 months in group 2, respectively. There was no significant difference between the 2 groups. In 17 cases (27%) in group 1 and 12 cases (19%) in group 2, the analgesic effect of the treatment was continued more than 12 months. This study suggests that treatment with 45-50°C radiofrequency application of the facet thyzotomy is equally as effective as the treatment at 60-65°C.