Studies indicating that drug abusers are high risks for violence are reported, and drug use is shown to characterize violent offenders. Findings reported by researchers in Baltimore and at the University of California at Los Angeles (UCLA) are discussed. The Baltimore researchers analyzed background factors and long-term crime patterns of 354 black and white male heroin addicts; the UCLA team's sample consisted of 753 white and Hispanic male heroin addicts. In contrast to their high levels of criminal activity while actively addicted, the addicts in each study showed significantly reduced criminality during periods of reduced use or nonaddiction. Self-report data gathered from 201 Harlem heroin addicts during 1980 to 1982 indicate that daily heroin users reported the highest crime rates; however, the economic harm per crime was relatively small. Estimates of 33 different types of economic harm imposed by street heroin abusers are presented; for example, the combined costs imposed on society by each daily heroin user in this study totalled about $55,000 annually. Finally, findings indicate that heroin and other drugs are so impure today that the notion that addicts have uncontrollable cravings that compel them to commit crimes to get money for drugs may no longer be valid. Fifteen references are included.