Three erroneous assumptions have influenced some illicit-drug control policy. One erroneous assumption is that addictive drugs are not different from many other consumed substances. This assumption underestimates the inherent neuro-behavioral properties of addictive drugs that produce compulsive, unhealthy consumption. A second erroneous assumption is that even a juvenile may learn to use addictive drugs reasonably and responsibly. This assumption overestimates the ability of the human neocortex to override the chemical stimuli induced by the drugs. A third erroneous assumption is that social acceptance and the commercial availability of addictive drugs would eliminate the social costs associated with their illegal trafficking. This ignores historical precedents and the results of epidemiological surveys that show the damaging effectives of the social acceptance of these drugs and their widespread use. A study of successful historical precedents in drug control policy indicates that the policy should concurrently curtail the supply of and the demand for illicit drugs. 38 references. (Author abstract modified)