This is a ten week, multicentre, double blind, randomised, placebo controlled parallel group study to evaluate the efficacy of Sativex® on urge incontinence associated with neurogenic unstable bladder. Multiple sclerosis patients with incontinence symptoms are screened to determine eligibility and complete a two-week baseline period. They then return for a further eligibility check, randomisation and initial dosing. Subjects titrate and self-medicate with study medication between study visits at weeks two and five. They will also complete efficacy assessments in their diary-books and at visits.