This 19 week, multicentre study was conducted in two phases. Phase A was a preliminary, single-blind four week treatment period to identify subjects with a capacity to respond to Sativex; eligible, consenting subjects entered a seven day screening period prior to returning to the study centre to begin a four week single-blind course of Sativex treatment. At the end of this phase, subjects' response to Sativex was assessed; those with the capacity to respond (i.e. at least a 20% reduction in mean 0-10 point numerical rating scale (NRS) spasticity score between screening and the end of the four week Phase A treatment) were eligible for entry into Phase B while those who did not respond took no further part in the study other than a follow up visit 14 days later.