This study presents and compares the drug policies in use in the United States, Sweden, and Italy to limit the use and abuse of substances such as marijuana, hashish, cocaine, heroin, and amphetamines. It also focuses on attempts to suppress the traffic in these drugs.A primary objective of Segre's work is theoretical: to evaluate and explain, by means of a comparative method applied to the study of individual cases, the respective level of success of these policies, measured according to conventional criteria. The aim of this comparison between Swedish drug policies (a positive case) and U.S. and Italian policies (negative cases) is to evaluate the effect of these policies on drug use. Segre comes to the general conclusion that there is a causal relationship between drug use and drug control. This is deduced from the association between Swedish policies and the limited diffusion of narcotics in Sweden on the one hand; and from the association between U.S. and Italian policies and the wide diffusion of these substances in the United States and in Italy, on the other hand. This study does not aim to give a complete explanation of the high or low use of narcotics. But what Segre does say is that the level of drug consumption could be a consequence of other causes, which are considered here not as independent variables but, on the contrary, as intervening variables.The literature in this field needs to dwell particularly on social and psychological causes. Examples are the influence of parents and peers, attitudes toward the use of drugs or abstention from them, the positive or negative images that persons have of themselves, and the possibility or, rather, the difficulty of establishing significant forms of interpersonal communication. This is a modest, serious contribution to the vexing issue of the causes of drug use in advanced societies.