This is a two week (two days baseline and two weeks treatment period), multicentre, double blind, randomised, placebo controlled, parallel group study to evaluate the efficacy of Sativex® and GW-2000-02 in subjects with cancer-related pain. Subjects are screened to determine eligibility and completed a two-day baseline period. Subjects then return to the centre for assessment, randomisation and dose introduction. All subjects are allowed to continue using all their current medications, provided that the dose remains stable throughout the study period. Their progress is reviewed after seven to 10 days and at the end of the study (day 14 to 20), or upon withdrawal. Subjects in this study are given the opportunity to be enrolled in an open label extension study (GWEXT0101).