evidence: Not long ago, discussion was focused on whether cannabis caused cancer. A thorough review by the US National Academies of Sciences, Engineering, and Medicine found moderate evidence of no statistical association between cannabis use and the development of lung and head and neck cancers.1 Limited evidence of a statistical association was found between cannabis use and the development of nonseminomatous testicular carcinomas without good support for a causative effect. Throughout the past few years, the pendulum has swung to the point where many patients with cancer diagnoses are convinced, mainly by internet testimonials, that cannabis, particularly highly concentrated oils or tinctures of Δ9-tetrahydrocannabinol (THC) and/or cannabidiol (CBD), may actually cure their cancers. What is the basis of this belief?