Although several critiques of the methodology of alcohol treatment outcome studies have been published, similar reviews of the methodology of drug treatment outcome studies are lacking. This paper reviews the methodology of drug treatment outcome studies published from 1993 through 1997 and draws comparisons with the most recent methodological review of alcohol treatment outcome studies. Each drug study was evaluated as to whether the following types of data were reported: (1) demographic, (2) drug use, (3) study characteristics, and (4) outcome and follow-up information. Although results for drug studies showed some areas of strength compared to alcohol studies, in general, the weaknesses were similar to or worse than in the alcohol field, including inadequate reporting of demographic and drug use variables. Weaknesses in follow-up procedures were particularly notable. Suggestions for improving the reporting of methodological and outcome variables for drug treatment outcome studies are discussed.