The debate regarding therapeutic use of cannabis is being confused by a lack of distinction between therapeutic and social use of cannabis. Separate consideration of therapeutic and social use would enable strategies to minimise any negative social impact of therapeutic use. For therapeutic use of cannabis to be considered on its own merits, greater emphasis needs to be placed on scientific evidence of therapeutic efficacy. At present the evidence is limited, it mostly relates to the use of synthetic cannabinoids, and much of it fails to compare cannabis with the best therapies available for the conditions of interest. Claims of therapeutic efficacy tend to be based on opinion and anecdote rather than the results of controlled studies. Further research is needed to clarify the potential therapeutic benefits, to enable claims of therapeutic use to be objectively assessed and to enable informed decisions to be made about the relative risks and benefits for any individual using cannabis for therapeutic purposes. Further research is required to clarify the efficacy of pure, synthetic cannabinoids compared to cannabis, the most effective route of administration, and the importance of delivering a known dose. The most likely value of cannabis is as an adjunct, rather than a replacement for, current medical approaches. The potential therapeutic benefits of cannabis will be greatest for those conditions where long-term cannabis use, with its attendant health risks, is not an issue and where the patient has the capacity to titrate dose against symptoms. There is sufficient evidence of potential therapeutic benefit to justify the facilitation of further research.