INTRODUCTION: Neurogenic detrusor overactivity (NDO) has a major impact on patients' quality of life and can lead to upper urinary tract complications. Intradetrusor botulinum toxin type A injections are administered as second-line treatment to these patients following the failure of anticholinergic agents. The aim of the DETOX 2 study is to propose a consensus definition of the failure of intradetrusor botulinum toxin injections for NDO in patients presenting spinal cord injury, spina bifida, or multiple sclerosis (MS) with self-catheterization. METHOD: This study followed the method adopted by the French National Authority for Health for recommendations by consensus. Based on a review of the literature and a preliminary survey, a steering committee compiled a questionnaire and selected a rating group comprising 16 experts from the Neuro-Urology Committee of the French Urology Association (cnuAFU) and Genulf. The experts were asked to complete the online questionnaire. At the end of the first round, all participants came together to discuss any disagreements and a second-round online questionnaire was completed to reach a consensus. RESULTS: Thirteen of the 16 experts approached completed both rounds of questionnaires. A strong consensus was reached for two proposals (median score = 9/10) which were therefore included in the definition from the first round: at least one repeat injection of the same botulinum toxin at the same dose must be given to rule out failure on technical grounds and a duration of efficacy <3 months must be considered a failure. At the end of round 2, a relative consensus was reached regarding the clinical criterion defining failure (median score = 7/10) and the urodynamic criterion of failure (median score = 8/10). An additional proposal was selected during this second round on the need for a voiding diary (median score = 8/10). CONCLUSION: The first consensus definition of failure of an intradetrusor injection of TB-A for NDO has been achieved with this study: persistence of detrusor overactivity with maximum detrusor pressures >40 cm H(2)O and/or a compliance issue and/or persistence of urinary incontinence and/or urgency and/or a number of daily self-catheterizations >8/day and/or efficacy <3 months. This study will help to standardize research on the failure of the intradetrusor botulinum toxin for NDO in clinical practice and clinical research.