The risk for cardiovascular disease, particularly congestive heart failure, is significantly higher in patients with type 2 diabetes mellitus than in individuals without diabetes. The presence of hyperglycemia has been associated with changes in the myocardium that are characteristic of diabetic cardiomyopathy and heart failure. Furthermore, insulin resistance may be associated with cardiomyopathy, even in the absence of hyperglycemia, and has been linked with cardiovascular remodeling. The association between heart failure and insulin resistance suggests that agents that improve insulin sensitivity, such as the thiazolidinediones (TZDs), are likely to be of cardiovascular benefit in patients with diabetes and heart failure. Although TZDs have beneficial cardiovascular effects in patients with type 2 diabetes, such as reducing blood pressure, improving endothelial function, and exerting potential antiatherosclerotic effects, one must be aware of the potential of these agents to cause edema or weight gain as a result of fluid retention and fat accumulation. These issues are of particular concern in patients with diabetes who have heart failure. However, the glycemic and cardiovascular benefits of TZDs may outweigh the potential problems of weight gain and fluid retention noted in some patients. Thus the risk-benefit ratio of using TZDs in patients who have diabetes and heart failure must be carefully considered in this patient population with comorbid disorders.