Randomized controlled trials and meta-analyses provide evidence for the efficacy of cognitive-behaviourally informed treatment (CBT) programmes for chronic pain. The current study aims to provide practice-based evidence for the effectiveness of CBT in routine clinical settings. Over a 10-year period 1013 pain patients were accepted into a 4 week in-patient pain management programme. Data from more than 800 patients was available at pre-treatment and at one month post-treatment and for around 600 patients at pre-treatment and at 9 months follow-up. Measures reported in this analysis were pain experience and interference, psychological distress (depression and anxiety), self-efficacy, catastrophizing, and walking. Change from pre-treatment to post-treatment and follow-up was assessed with conventional statistical tests, the computation of effect sizes and by the reliable change index (RCI) and clinically significant change (CSC) methodology. These analyses provide evidence of statistical improvement at post-treatment and follow-up and the RCI/CSC methodology suggested that between 1 in 3 and 1 in 7 (depending on the outcome measure) achieved clinically significant gains. There was also evidence that a small percentage of patients (1-2%) reliably deteriorated during the period of treatment. The limitations in the inferences that can be drawn from this study and of the methodology are discussed. A case is made for the application of benchmarking methods using data from RCTs in order to more fully evaluate practice and to generate better quality practice based evidence.