BACKGROUND-: The economic outcomes of clinical management strategies are important in assessing their value to patients. METHODS AND RESULTS-: Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) randomized patients with type 2 diabetes mellitus and angiographically documented, stable coronary disease to strategies of (1) prompt revascularization versus medical therapy with delayed revascularization as needed to relieve symptoms and (2) insulin sensitization versus insulin provision. Before randomization, the physician declared whether coronary artery bypass grafting or percutaneous coronary intervention would be used if the patient were assigned to revascularization. We followed 2005 patients for medical utilization and costs and assessed the cost-effectiveness of these management strategies. Medical costs were higher for revascularization than medical therapy, with a significant interaction with the intended method of revascularization (P<0.0001). In the coronary artery bypass grafting stratum, 4-year costs were $80 900 for revascularization versus $60 600 for medical therapy (P<0.0001). In the percutaneous coronary intervention stratum, costs were $73 400 for revascularization versus $67 800 for medical therapy (P<0.02). Costs also were higher for insulin sensitization ($71 300) versus insulin provision ($70 200). Other factors that significantly (P<0.05) and independently increased cost included insulin use and dose at baseline, female sex, white race, body mass index ≥ 30, and lbuminuria. Cost-effectiveness based on 4-year data favored the strategy of medical therapy over prompt revascularization and the strateg of insulin provision over insulin sensitization. Lifetime projections of cost-effectiveness showed that medical theray was cost-effective compared with revascularization in the percutaneous coronary intervention stratum ($600 per life-year added) with high confidence. Lifetime projections suggest that revascularization may be cost-effective in the coronary artery bypass grafting stratum ($47 000 per life-year added) but with lower confidence. CONCLUSIONS-: Prompt coronary revascularization significantly increases costs among patients with type 2 diabetes mellitus and stable coronary disease. The strategy of medical therapy (with delayed revascularization as needed) appears to be cost-effective compared with the strategy of prompt coronary revascularization among patients identified a priori as suitable for percutaneous coronary intervention. © 2009 American Heart Association, Inc.