Natural cannabis (?9-THC, tetrahidrokannabinol) is derived from the plant called Cannabis Sativa. Acute effects of cannabis include euphoria, relaxation, subjective slowing in time perception, dizziness, analgesia, difficulties in memory and problem solving, ataxia, tachycardia, systolic hypertension, postural hypotension, increased apatite, anxiety, paranoid thoughts and depression. Cannabis can cause dependence and withdrawal. DSM-5 lists withdrawal symptoms as: anger, irritability or feelings of aggression; depressed mood; feelings of restlessness; loss of appetite; insomnia; feelings of anxiety or nervousness; physical symptoms of withdrawal, such as headache, stomach pains, increased sweating, fever, chills or shakiness. Cannabis is also known to have some therapeutic effects such as antiemetic in cancer patients, spasmolytic in multiple sclerosis (MS), appetizer in AIDS, anti-inşammatory in rheumatoid arthritis, antidiarrheal in Crohn’s disease and also useful in neuropathic pain, glaucoma and movement disorders. Cannabis acts on cannabinoid receptors (CB1 and CB2). Main endogen cannabinoids are anandamide and arachidonilglyserol. Marijuana contains approximately 60 cannabinoids. ?9-tetrahydrocannabinol which is the most effective one activates mesolimbic dopaminergic system so that it affects reward and reinforcement mechanism. Today there are a few medications containing cannabinoids used for medical purposes: Dronabinol (Marinol®), Nabilone (Cesamet ®), Nabiximols (Sativex®) and medical marijuana. Nabiximols (Sativex® oral spray) was approved for decreasing stress, muscle rigidity and pain in MS. It can be used in moderate to severe cases that are refractory to other spasmolytic medications. Good results have also been reported with neuropathic pain, overactive bladder, cancer pain and Tourette syndrome. Medical uses of cannabis have led investigators to search for synthetic cannabinoids (SC). These compounds which were initially used for analgesia have THC like effects. They were not marketed as medicine due to their psychoactive properties, however, their abuse spread rapidly. These compounds are marketed on the street with names such as Spice, K2, Genie in Europe and USA. In Turkey they have street names such as Bonzai, Jamaica and Jamaican Gold. Their chemical structure is quite different than THC. They are designated with chemical formulas like JWH-018, JWH-073, HU-210, CP-47, CP-497, JWH-018 and a new one is added every day. They were officially registered as illegal substances on 13.02.2011 in Turkey. Their cannabinoid receptor (CB1R) affinity and activity is higher than those of THC. They have a larger effect size and more frequent and more severe adverse effects compared to THC. Their effect starts more rapidly but lasts shorter. There is risk of intoxication depending on amount and degree of purity. Their adverse effects which are not seen or less frequently seen with natural THC include convulsions, anxiety, aggressiveness, muscle rigidity and confusion. Their abuse has been popular rapidly due to their easy access and being undetectable in routine urine screens. SC’s have been reported to cause dependence and physiological withdrawal. Poison Control Center data in USA report agitation, confusion, hallucination, hypertension, myocardial ischemia, heart attack linked to the use of SC. Toxic effects usually resolve in 3-4 hours. There are many case reports of convulsions due to SC. They are generalized tonic clonic (GTC), usually multiple and don’t leave sequel. Emergency department physicians should suspect from SC abuse in young males who apply with first time GTC seizure. In cases of new and sudden onset psychosis that are on urine drug screen follow-up or in cases who demonstrate signs of cannabis abuse but give negative urine test, SC abuse should be suspected. SC has also been reported to cause some other serious medical adverse effects like acute kidney failure, acute loss of vision and Wernike Syndrome.