The Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) is a National Institutes of Health (NIH)-sponsored randomized clinical trial that evaluates treatment efficacy for patients with type 2 diabetes mellitus and angiographically documented stable coronary artery disease. Using a 2 x 2 factorial design, BARI 2D compares revascularization combined with aggressive medical treatment versus aggressive medical treatment alone; simultaneously, BARI 2D compares 2 glycemic control strategies, insulin sensitization versus insulin provision. All patients have goals of glycosylated hemoglobin values <7.0% and uniform control of hypertension, dyslipidemia, and obesity following recommended medical guidelines. The primary end point of BARI 2D is all-cause 5-year mortality analyzed by intention to treat, and the principal secondary end point is the combination of death, myocardial infarction, and stroke. A total of 2,368 patients have been enrolled at 49 clinical centers throughout North America, South America, and Europe. The study enrollment period was January 2001 through March 2005, and the patient treatment and follow-up phase is expected to extend at least through May 2007. Participants are treated at the local BARI 2D clinical sites on a monthly basis for the first 6 months and then every 3 months until the end of the study. Within BARI 2D, central management centers oversee the control of glycemia, plasma lipid levels, hypertension, and obesity. The randomized clinical trial collects data on patient symptoms, clinical measurements, medications, and clinical events as well as data from centralized evaluations of angiograms, electrocardiograms, nuclear stress tests, blood and urine specimens, and relative economic costs.