Effectiveness trials are an important step in the scientific process of developing and evaluating behavioral treatments. The focus on effectiveness research presents a different set of requirements on the research design when compared with efficacy studies. The choice of a control condition has many implications for a clinical trial's internal and external validity. The purpose of this article was to provide a discussion of the issues involved in choosing a control group for effectiveness trials of behavioral interventions in substance abuse treatment. The authors provide a description of four trial designs and a discussion of the advantages and disadvantages of each.