Aims  To describe the eligibility criteria (i.e. study participant inclusion and exclusion rules) employed in alcohol treatment outcome research and to identify predictors of their use.

Design  The eligibility criteria of 683 alcohol treatment outcome studies conducted between 1970 and 1998 were coded reliably into 14 general categories. Predictors of the use of eligibility criteria were then examined.

Findings  Patients were most often ruled ineligible for research studies because of their level of alcohol problems (39.1% of studies), comorbid psychiatric problems (37.8%),  past  or  concurrent  utilization  of  alcohol  treatment  (31.8%),  co-occurring  medical  conditions  (31.6%),  and  because  they  were  deemed  non-compliant and unmotivated (31.5%). The number of eligibility criteria employed in studies increased from the 1970s through the 1990s, and was positively associated with funding from the US National Institute of Alcohol Abuse and Alcoholism (NIAAA) and from the private sector, lack of an inpatient/residential treatment condition, presence of a pharmacotherapy, and use of a randomized, multiple-condition design. Principal investigators with doctoral degrees used more eligibility criteria than those with lower degrees.

Conclusion  Participant eligibility criteria are extensively employed in alcohol treatment outcome research, and vary significantly across historical periods, funders and research designs. Researchers should report the details of subject eligibility criteria and excluded patients more fully, and, evaluate how eligibility criteria affect the cost, feasibility, and generalizability of treatment outcome research.