The study will compare the effect of atorvastatin to the effect of fenofibrate on endothelial function in patients with diabetes mellitus or the metabolic syndrome. The study is a double blind, placebo controlled, crossover study with the order of treatment randomized. Patients will receive each treatment for 8 weeks with a 1 week rest period between treatment periods. Endothelial function will be tested using non-invasive techniques before and after each treatments. A total of 40 subjects with diabetes or the metabolic syndrome will be enrolled at Boston Medical Center.