OBJECTIVES: In the context of a regional HTA system in the South West of the UK, we assessed the potntial cost utility of Sativex relative to oral anti-spasticity agents in MS METHODS: A decision-analytic model was developed to estimate cost-effectiveness in a cohort of adults who have moderate to severe spasticity due to MS.  A three state Markov model was used: in response; response lost; death.  Transition probabilities were obtained from a systematic review of the effectiveness of Sativex.  The study cohort was aged 50 years (60% women).  Cycle length was four weeks and time horizon five years.  Costs were assessed from the perspective of the health care system.  In some cases, treatment with botulinum toxin or implantation of a baclofen intrathecal pump may be considered and these options were explored in sensitivity analysis.  Utility data was obtained from one of the trials of Sativex using the EQ5D.  Extensive one way, threshold and probabilistic approaches were taken in analysis of uncertainty. RESULTS: The base case ICER was £49,300 per QALY with a probability of cost effectiveness at a willingness to pay of £30,000 per QALY of around 10%.  Results were sensitive to the amount of Sativex per day – at the minimum dose (4 sprays) the ICER was around £25,000 per QALY but at the maximum (12 sprays) was nearly £70,000 per QALY.  Threshold analysis suggests that for the mean dosage given in RCTs to be considered cost effective, a 40% reduction in price is needed.  Including a proportion of people using more expensive current treatments improved expected cost effectiveness. CONCLUSIONS: Sativex is unlikely to be considered a cost effective treatment for most people who would meet the licensed indication for treatment in the UK at this time.