INTRODUCTION: Little is known about the extent and patterns of cannabis use in people with multiple sclerosis (MS). METHODS: MS patients attending neurology outpatient clinics at two hospitals in London and one in Kent, UK completed a questionnaire. RESULTS: Questionnaires were completed by 254/337 (75%) MS patients. Forty-three per cent had used cannabis at some stage (ever users). Of these, 68% (75/110) had used cannabis to alleviate symptoms of MS (MS-related cannabis use). Forty-six (18%) had used cannabis in the last month (current users), of whom 12% (31/254) had used it for symptom relief. Being married or having a long-term partner, tobacco smokers and increasing disability were independent risk factors for MS-related cannabis use. Compared to patients who could walk unaided, cannabis use was more likely in those who were chair-bound (adjusted OR 2.47; 1.10-5.56) or only able to walk with an aid (adjusted OR 1.56; 0.90-3.60). Pain and spasms were common reasons for cannabis use. Seventy-one per cent of individuals who had never used cannabis said they would try the drug if it were available on prescription. CONCLUSION: A large proportion of MS patients had tried cannabis for symptom control, however current use was small. A subgroup with greater disability appears to derive some symptomatic benefit.