Background: On the basis of observational data, intradiscal electrothermal anuloplasty (IDETA) has been implemented as a treatment for back pain resulting from internal disc disruption. Purpose: To assess the efficacy of IDETA. Study design: Prospective cohort study with comparison group and 2-year follow-up. Patient sample: Of 53 patients who satisfied the diagnostic criteria for internal disc disruption, 36 were allocated to a treatment group and 17 to a comparison group, according to whether their insurer approved treatment with IDETA. Outcome measures: Outcomes were assessed in terms of relief of pain, return to work and use of opioids to treat persisting pain. Methods: The treatment group underwent IDETA. The comparison group underwent a conventional rehabilitation program. Outcomes were assessed at 3 months, 12 months and 2 years after treatment. Results: As a group, the comparison patients exhibited no significant improvement in their pain at any time. One was partially relieved, but no patient was completely relieved at either 12 or 24 months. The patients treated with IDETA exhibited significant improvements in their median pain scores, which were sustained at 12 and 24 months. At 24 months, 54% of these patients had achieved at least 50% relief of their pain, no longer used opioids and were at work. Seven patients (20%) were totally free of pain and at work at 24 months. Conclusions: The long-term results of IDETA are stable and enduring. It is not universally successful, but 54% of patients can reduce their pain by half, and one in five patients can expect to achieve complete relief of their pain.