The ability to reliably detect heavy alcohol use is important in both clinical and research populations. The current study evaluates the utility of the newest method of measuring carbohydrate deficient transferrin (CDT) in monitoring the abstinence during a treatment outcome study. Blood from 40 alcohol dependent individuals was obtained at baseline and at weeks 4, 8, and 12 of treatment. Differences in percent of baseline GGT and %CDT levels were analyzed in people who remained abstinent throughout treatment (abstainers) and in those who consumed alcohol during treatment (drinkers). There was a significant decrease in the percent of baseline %CDT levels in the subjects who abstained at week 4 and a trend at weeks 8 and 12. Conversely, there were no significant differences in percent of baseline GGT levels between drinkers and abstainers at any time point. Although small in nature, this study provides preliminary evidence for the use of the relatively new Biorad %CDT assay to monitor drinking status during treatment outcome studies. This study is also consistent with previously reported findings that GGT appears to be less sensitive than %CDT in detecting the consumption of alcohol. A larger trial focusing on sex differences in the utility of % CDT to monitor outcome would be of interest.