Background: Historically, older adults, women and minorities have been underrepresented in clinical trials. Exclusions or underrepresen­tation limit the generalizability of study findings to these patient populations in need of treatment. This poses a challenge for evidence-based practice as medicines may not have the same safety, efficacy or effectiveness in older adults, women, or certain ethnic groups. Objective: To determine the proportion of older adults, women and ethnic minorities in published clinical trials of drug therapy for the treatment of type 2 diabetes (DM2) and how this enrollment compares with disease prevalence in the United States. Methods: We searched PubMed for randomized clinical trials (RCTs) evaluating hypoglycemic agents for the treatment of type 2 diabetes from 2003 to 2007. Unpublished and non-English language manuscripts were excluded. Data on year of publication, funding, trial location, sample size, intervention, inclusion and exclusion criteria, demographics and characteristics of the study sample, and primary outcome measured were extracted by two independent reviewers. Proportions of older adults (age ≥65 or age ≥75), women, and ethnic groups enrolled in the trial population were compared to the prevalence of DM2 in the United States during 2005. Results: Participants in 529 RCTs of drug therapy for DM2 are significantly different from patients with DM2 in the US population. Older adults ≥65 years, blacks, Hispanics, and American Indian/Alaskan Natives are less likely to be enrolled in RCTs (Table 1). In addition, demographic characteristics of trial participants and outcomes stratified by age, gender or ethnicity were often poorly reported or not reported at all. Conclusions: Underrepresentation of older adults and ethnic minorities impairs the generalizability of RCT results for treatment of DM2 in these high risk groups. Adequate representation of these populations relative to their disease prevalence is necessary to provide a better evidence-base for the treatment of DM2 and promote health equity.