Introduction: Legal access to marijuana, most frequently as “medical marijuana,” is becoming more common in the United States, but most states do not specify sickle cell disease as a qualifying condition. We were aware that some of our patients living with sickle cell disease used illicit marijuana, and we sought more information about this. Materials and Methods: We practice at an urban, academic medical center and provide primary, secondary, and tertiary care for ∼130 adults living with sickle cell disease. We surveyed our patients with a brief, anonymous, paper-and-pen instrument. We reviewed institutional records for clinically driven urine drug testing. We tracked patient requests for certification for medical marijuana. Results: Among 58 patients surveyed, 42% reported marijuana use within the past 2 years. Among users, most endorsed five medicinal indications; a minority reported recreational use. Among 57 patients who had at least one urine drug test, 18% tested positive for cannabinoids only, 12% tested positive for cocaine and/or phencyclidine only, and 5% tested positive for both cannabinoids and cocaine/phencyclidine. Subsequent to these studies, sickle cell disease became a qualifying condition for medical marijuana in our state. In the interval ∼1.5 years, 44 patients have requested certification. Conclusion: Our findings and those of others create a rationale for research into the possible therapeutic effects of marijuana or cannabinoids, the presumed active constituents of marijuana, in sickle cell disease. Explicit inclusion of sickle cell disease as a qualifying condition for medical marijuana might reduce illicit marijuana use and related risks and costs to both persons living with sickle cell disease and society.