Background: The marijuana plant Cannabis has been used for centuries in the medicinal treatment of many disorders and is still the subject of medical research and public debate. Cannabinoids have been purported to alleviate a variety of neurological conditions such as MS-related symptoms including spasticity, pain, tremor and bladder dysfunction. Other neurological conditions like chronic intractable pain, dystonic movement disorders and Tourette's Syndrome were all reported to be alleviated by cannabis use. Cannabis has been used to treat anorexia in AIDS and cancer patients. In gastroenterology cannabis has been used to treat symptoms and diseases including anorexia, emesis, abdominal pain, gastroenteritis, diarrhoea, intestinal inflammation and diabetic gastroparesis.

Cannabinoids have also a profound anti inflammatory effect, mainly through the CB2 receptor. Cell mediated immunity may be impaired in chronic marijuana users. And a potent anti-inflammatory effect of cannabis was observed in rats . Studying the functional roles of the endocannabinoid system in immune modulation reveals that there are no major immune events which do not involve the endocannabinoid system. Cannabinoids shift the balance of pro-inflammatory cytokines and anti-inflammatory cytokines towards the T-helper cell type 2 profiles (Th2 phenotype), and suppress cell-mediated immunity whereas humoral immunity may be enhanced. They are therefore used for various inflammatory conditions including rheumatoid arthritis and asthma. In a mouse model of colitis cannabinoids were found to ameliorate inflammation and there are many anecdotal reports about the effect of cannabis in inflammatory bowel disease. However, there are no methodical reports of the effect of cannabis on inflammatory bowel disease. The aim of the proposed study is to examine in a double blind placebo controlled fashion the effect of smoking cannabis on disease activity in patients with IBD.

Inclusion Criteria:

1. Patients with a diagnosis IBD at least 3 months before recruitment will be eligible to the study.
2. Patients with active disease who are resistant to either 5 ASA, steroids or immunomodulators, or who can not receive those drugs due to adverse reactions will be offered the possibility of smoking cannabis at a dose of two cigarettes a day which will contain either regular cannabis or pre treated cannabis as placebo.
3. Disease activity index of either CDAI of more then 200 in Crohn's disease or Mayo score above 3 in UC.
4. Age above 20.

Exclusion Criteria:

1. Patients with a known mental disorder
2. Patients who are deemed to be at a high risk of abuse or addiction to the study drug.
3. Pregnant women
4. Patients who are sensitive to any of the ingredients of the study medication.
5. Patients who are unable to give informed consent.
6. Patients who may need surgery in the near future.