Most clinical trials of lipid intervention and coronary artery disease prevention have been conducted in study populations that exclude diabetic individuals. Three trials have conducted post hoc analyses of their diabetic subgroups. One of these was a primary intervention trial with gemfibrozil (Helsinki Heart Study). Although this trial found a reduction in coronary events, the numbers were too small to reach significance. The two other trials (the Scandinavian Simvastatin Survival Study [4S] and Cholesterol and Recurrent Events Trial [CARE]) were secondary intervention trials conducted with hydroxymethylglutaryl-CoA reductase inhibitors, simvastatin, and pravastatin. Both of these trials found a reduction in coronary events. Although these two trials present the strongest evidence in support of the clinical benefits of lipid reduction in diabetes, they must be interpreted with caution. They are post hoc subgroup analyses, they looked at mainly hypercholesterolemic populations, and they are secondary intervention studies. Four studies aimed at testing the "lipid hypothesis" specifically in diabetes are currently under way. Three of these studies (Fenofibrate Intervention and Event Lowering in Diabetes [FIELD], Collaborative Atorvastatin Diabetes Study [CARDS], and Lipids in Diabetes Study [LDS]) are primary prevention trials, with clinical events as the primary end point. FIELD uses micronized fenofibrate, CARDS uses atorvastatin, and LDS uses both micronized fenofibrate and cerivastatin alone or in combination. These trials are in the early stages of starting or recruiting. One study (Diabetes Atherosclerosis Intervention Study [DAIS]) using micronized fenofibrate is nearing completion. It is an angiographic study that combines those with and without preexisting clinical coronary disease.