Although categorization of marijuana as a Schedule I controlled substance can make broad-based research difficult, marijuana, THC, and cannabinoid pharmaceuticals have been studied for a number of medical applications, including the treatment of nausea, pain, anorexia and weight loss, seizures, spasticity, and glaucoma. This review concentrates on the uses of marijuana and cannabinoids that most directly impact the patient with cancer: nausea, pain, and anorexia and weight loss. This is followed by a short review of clinical trials of cannabinoids as anticancer agents.