The debate about the legal status of cannabis and its effect on health has polarised public opinion. In the absence of credible non partisan advice, health education about cannabis has been neglected because of uncertainty about what information to present. This paper summarises likely adverse acute and chronic health effects of cannabis that emerged from a peer-reviewed analysis of the research literature undertaken for the National Task Force on Cannabis. From this review, suggestions are offered concerning advice that family physicians can give to their patients about the health risks of using cannabis.