Ethnographic studies, which supplied much of the data for this study, use intensive field observation and interviews to obtain data in the natural setting of the behaviors under study. Such studies use nonrandomly selected, purposive, or snowball samples. Ethnographic studies are useful in obtaining data on consensual crimes (no victim incentive to report the crime). Data indicate that drug dealers often share background characteristics with their clients. Drug use among drug dealers varies from nonuse to daily use, but the proportion of dealers who use drugs is difficult to determine. Among frequent users of heroin and cocaine, drug dealing or prostitution may be a regular activity. Although drug use may not be a precipitating factor in drug dealing and prostitution, it is a significant factor in continued involvement in these activities. Continued drug use is the single best predictor of a criminal career for drug-using offenders, and disruption of drug use significantly reduces the crime rate characteristic of heavy drug users. This occurs because the financial burden of heavy drug use is reduced and the criminogenic influences of the drug-using lifestyle are weakened. 90 references