AbstractHarm reduction attempts to reduce the adverse consequences of drug use among persons who continue to use drugs. It developed in response to the excesses of a “zero tolerance approach”. Harm reduction emphasizes practical rather than idealized goals. It has been expanded from illicit drugs to legal drugs and is grounded in the evolving public health and advocacy movements. Harm reduction has proved to be effective and it has gained increasing official acceptance; for example, it is now the basis of Canada's Drug Strategy. However, the concept is still poorly defined, as virtually any drug policy or programme, even abstinence‐oriented programmes, attempt to reduce drug‐related harm. The principle feature of harm reduction is the acceptance of the fact that some drug users cannot be expected to cease their drug use at the present time. Harm reduction is neutral about the long term goals of intervention while according a high priority to short‐term realizable goals. Harm reduction should be neutral about legalization. The essence of the concept is to ameliorate adverse consequences of drug use while, at least in the short term, drug use continues.