SummaryHumans have always used mind-altering drugs. However, in 1961 the United Nations approved the Single Convention, under which the production, sale or possession of a number of drugs, including heroin, cocaine, ecstasy and cannabis, became illegal. The prohibitionist regime was then introduced by most countries around the world and has substantially remained in place ever since. Some countries, particularly those in Latin America, have never criminalised the use of cannabis. A small number of countries have introduced more liberal policies. This article examines the evidence of the consequences of policy liberalisation and argues that there is now a clear case for every country to examine its drug policies and to introduce evidence-based policies with a public health focus.Declaration of interestNone.