Part I identifies what is at stake in marijuana consumption and trafficking, quantifies the size of the problem, and discusses the criteria with which to judge a policy recommendation. Part II develops a theory of drug trafficking and its response to varying levels of enforcement pressure, applying the theory to the early years of the increased Federal anti-marijuana enforcement effort of the 1980's. Part III evaluates that effort and discusses the policy options available for the future. The book concludes that any feasible increase in Federal enforcement will produce only slight and severely qualified benefits in reducing drug abuse. Higher prices will cause consumers to cut back only modestly in marijuana use and encourage use of more potent forms of marijuana and the use of more dangerous drugs. Increased enforcement will also make the market more lucrative for traffickers and strengthen the hand of those criminal groups best able to resist and adjust to increased enforcement efforts. The book recommends reduced enforcement as a less risky alternative than either legalization or decriminalization. 80-item bibliography, chapter notes, subject index.