Many patients with IBD report that smoking marihuana ameliorated their symptoms, but there are no clinical studies investigating that observation. We have recently published the first reported observation of use of medical cannabis in Crohn's disease. In our study, of 30 patients, 21 improved significantly after treatment with cannabis. The average Harvey Bradshaw index improved from 14 ± 6.7 to 7 ± 4.7 (P < 0.001). Number of bowel movements was reduced from an average of eight a day to five a day and the need for other medication, particularly steroids, was significantly reduced. In view of those results we conducted a double blind placebo controlled trial in 20 active Crohn's disease patients. Patients with a Crohn's Disease Activity Index (CDAI)>200 who did not respond to steroids, immunosuppressants or anti-TNF were randomized to receive 2 cigarettes of cannabis or placebo daily. Each cigarette contained 0.5 g of cannabis, corresponding to 11.5mg Tetrahydrocannabinol (THC). The placebo contained cannabis leaves from which THC was extracted. During treatment the CDAI changed in the cannabis group from 358 ± 99 to 139±111 (p<0.05) and in the placebo group from 373 ± 94 to 306±143 (p=Non significant). Five patients in the cannabis group and one in the placebo group went into complete remission (CDAI <100). Three steroid dependent patients in the cannabis group stopped steroids during the study. Patients reported improved appetite and sleep, with no serious side effects.