Research on drug abuse treatment indicates significant declines in drug use and criminal behavior by drug-dependent clients as a result of treatment. Basic questions remain, however, regarding whether such improvements would have occurred without treatment, due to maturation, regression to the mean, or other nontreatment influences. Four structural features are crucial in designing and implementing treatment programs. First, the intervention period must be lengthy, since drug dependence is typically a chronically relapsing condition. Second, programs must initially provide a significant level of structure, such as a residential stay in a controlled setting or very close monitoring in an outpatient setting. Third, effective programs are flexible; no absolute mandates should determine client management. Fourth, any intervention program must undergo regular evaluation to determine its impact and whether changing client characteristics require compensatory program changes. 2 tables, appended outline of treatment benefits, and 210 references