The literature on inpatient and outpatient treatment of alcohol and drug abusers is reviewed. In addition, attrition as a major factor in treatment is examined. While several hypothesized advantages for both inpatient and outpatient treatment are advanced, it is pointed out that, because of methodological and situational differences among the studies, comparisons are difficult and risky to make. After suggesting that there is little evidence to cause one to tout either inpatient or outpatient treatment based on relative effectiveness, it is proposed that a flexible treatment program utilizing both inpatient and outpatient treatment with a focus on reducing attrition is most likely to maximize effectiveness.