Drug smuggling, drug manufacturing, drug selling, drug possession, and drug use are in themselves crimes. Drug-related offenses are those to which a drug's pharmacological effects contribute, such as violent behavior due to diminished behavioral control and paranoid delusions; they are also offenses motivated by the user's need to obtain money to support continued drug use, as well as offenses associated with efforts to advance a drug-dealing enterprise, such as violence against rival drug dealers. A drug-using lifestyle is one in which the likelihood and frequency of involvement in illegal activity increase because drug users may not participate in the legitimate economy and are exposed to situations that encourage crime. Such a lifestyle includes an emphasis on short-term goals supported by illegal activities, opportunities to offend that result from contacts with offenders and illegal markets, and the acquiring of criminal skills learned from other offenders. Overall, the evidence shows that drug users are more likely than nonusers to commit crimes, that arrestees are frequently under the influence of a drug at the time they committed the charged offense, and that drugs generate violence. An assessment of the nature and extent of the influence of drugs on crime requires that reliable information about the offense and the offender be available and that definitions be consistent. 6 tables and 7 references