Cannabinoid hyperemesis is a syndrome characterized by severe nausea and hyperemesis associated with chronic marijuana abuse and marked by compulsive bathing habits, which temporarily alleviate symptoms. We describe the syndrome in 4 adult patients for whom extensive gastrointestinal evalua- Cannabinoid hyperemesis was first described by Allen 1 in a 2004 case series of 9 patients in Australia, and it is defined as excessive marijuana use associated with cyclical vomiting and abdominal pain. We describe 4 cases of chronic cyclical vomiting in adults who habitually smoked marijuana. We also propose a mechanism to explain the compulsive bathing in warm water that characteristically brings temporary relief of symptoms. Case Reports Patient 1A 20-year-old African-American man presented to the emergency department (ED); he had been having frequent episodes of nausea and vomiting for 8 months and indicated that warm baths provided relief of his symptoms. He denied any medical or surgical history. His only medication was promethazine. An abdominal ultrasound and computerized tomography (CT) scans of his abdomen and pelvis with and without contrast were negative; his vital signs were normal, and his abdomen was soft and was not tender. He admitted to smoking marijuana daily and smoking 5 cigars per day for at least the past 4 years. Laboratory data included a white blood cell count of 11,700 cells/L with normal complete blood count (CBC), basic metabolic profile (BMP), hepatic profile, and lipase. Urine drug screen revealed only cannabinoids. The patient was admitted for rehydration, antiemetics, and evaluation. Upper endoscopy showed very mild esophagitis and gastritis with negative biopsies for Heliobacter pylori. During the patient's hospitalization, he took long showers multiple times each day; furthermore, it was difficult for the physicians to convince the patient to exit the shower for examination.The physician stressed complete abstinence from marijuana, and the patient was placed on a short course of omeprazole. The patient was contacted 2 months after discharge and reported improvement in symptoms since marijuana cessation.