Cannabis is now (2023) approved for medical use in forty-one states, and for recreational purposes in twenty-three of those states. In the future, other states are certain to adopt similar laws. Considering that cannabis used for medicinal purposes is ingested or smoked, and that it is often smoked when used for recreational purposes, the effect of cannabis on the oral cavity is a concern for oral health care providers who will be seeing an increasing number of users. This Quality Resource Guide (QRG), using an evidence-based approach: reviews the diseases and disorders for which medical marijuana has been used; discusses the potential effects of cannabis use on oral health (oral mucosa, dental caries and the periodontal diseases); analyzes its role as a risk factor for oral cancer; examines the limitations and shortcomings of studies that have examined the relationship of cannabis use to oral disease; and explores the issues surrounding the obtainment of accurate patient histories regarding cannabis/marijuana use. This QRG will serve as an important resource for the dentist, and all members of the office staff, as they assess and provide oral health therapy in today’s world.