Marijuana has been smoked for its medicinal properties for centuries. Preclinical, clinical, and anecdotal reports suggest numerous potential medical uses for marijuana. Although the indications for some conditions (e.g., HIV wasting and chemotherapy-induced nausea and vomiting) have been well documented, less information is available about other potential medical uses. Additional research is needed to clarify marijuana's therapeutic properties and determine standard and optimal doses and routes of delivery. Unfortunately, research expansion has been hindered by a complicated federal approval process, limited availability of research-grade marijuana, and the debate over legalization. Marijuana's categorization as a Schedule I controlled substance raises significant concerns for researchers, physicians, and patients.