Background: Ketamine has been used in chronic pain management for a number of years.It exhibits analgesic actions at many sites, both centrally and peripherally.These include NDMA, kainite, GABA, receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, inhibition of voltage gated Na+ and K+ channels and serotonin and doparnine re-uptake.Ketamine reverses opioid tolerance by an interaction between NMDA receptors, the nitric oxide pathway and μ-opioid receptors.This results in blocking central sensitization that is causing central pain.Objective: This study was performed to evaluate whether a 5 day intravenous ketamine infusion was able to reduce pain levels and reduce opioid requirements in patients attending the RPAH Pain Clinic between 2007 and 2011, with chronic, non-cancer pain.Methods: Retrospective study of 52 patient records with 45 patients taking high doses of opioids and 7 patients were taking high doses of anti-neuropathic medications, with no reduction of the pain intensity.Visual analogue scale (VAS) pain scores were recorded.Results: There was significant reduction in pain intensity from a mean of 6.38 before ketamine to 4.6 (p<0.005).Only 5 patients had no change in the VAS.The ketamine infusion was tolerated well with only 1 patient prematurely ceasing the infusion.46% of patients experienced lightheadness or dizziness, but did not need to discontinue the infusion.Conclusion: This study provides strong evidence that a 5 day intravenous ketamine infusion has the potential to reduce pain in the short term, in even chronic pain patients who have responded poorly to treatment.The analysis supports a prospective study to measure the duration of effect of ketamine and also measure of quality of life changes.