Research for this paper developed six major findings: (1) Studies of persons who have been arrested and processed in the criminal justice system, unapprehended criminals, and persons in drug treatment programs indicate that higher levels of illicit drug use (especially of heroin and cocaine) are accompanied by higher levels of criminal activity, both drug distribution offenses and other serious offenses not related to drugs. (2) Among youth in the general population, the small subset who use cocaine, heroin or pills for nonmedical reasons account for a disproportionate amount of all juvenile crime. (3) Persons in the United States who use illicit drugs enough to have associated legal problems tend to be so enmeshed in other deviance and adjustment problems as to make difficult, if not impossible, determination of the exact sequence of the onset of drug use and criminal behavior. (4) Chronic users of heroin and cocaine who are repeatedly processed through the criminal justice system typically engage in a variety of crimes and distribution activities. (5) Treatment programs can reduce drug abuse and crime if the offender remains in treatment. (6) Urinalysis tests appear to be an effective tool for identifying drug-using arrestees, but further research is needed on how to use this information. Tables, appendixes, references