OBJECTIVES: This study assesses the cost-effectiveness of Intradiscal electrothermal therapy (IDET) relative to femoral ring allografts (FRA), a form of spinal fusion, for discogenic back pain. Spinal fusion is an established surgical treatment; IDET is less invasive and potentially less costly. McKenna (2005) reported an RCT comparing FRA and titanium cage (TC). Based on this trial, Freeman (2007) demonstrated the relative cost-effectiveness of FRA. The present study used the same FRA cohort for evaluating the cost-effectiveness of IDET vs. FRA.  METHODS: Patient-level data on resource use up to 24 months and SF-36 (measured pre-operatively and at 6, 12, 24 months) were available for all 37 FRA patients of McKenna (2005) trial. Comparable data were collected prospectively on 85 patients treated with IDET at Queen’s Medical Centre, Nottingham. Data variables were matched between the two patient groups.  Utility scores were produced from SF-36 by using Brazier (2004) algorithm. Differential costs and utilities, together with 95% confidence intervals, were estimated using bias corrected and accelerated bootstrapping. RESULTS: There were no significant differences between the groups in age, gender or SF-36 domain scores, except physical function (p=0.004) and mental health (p=0.021), both lower in the FRA group. Baseline utility scores were lower in the FRA group (0.48 vs. 0.52, p=0.03).On the central assumptions, the expected cost per patient was lower with IDET by £3713 (95% CI -£2684 to -£4742).  The differential QALYs of IDET vs. FRA (adjusted for preoperative utilities) were 0.03 (95% CI -0.07 to 0.12).  At a willingness-to-pay (WTP) threshold of £20,000 per QALY, the net health benefit (NHB) of IDET was 0.21 and the probability of IDET being cost-effective was 1. If the WTP threshold was £30K/QALY, the NHB was 0.15 (probability cost-effective = 0.997). CONCLUSIONS: IDET offers a cost-effective alternative to spinal fusion. IDET has the advantage that it is less invasive and can be performed as a day-case procedure