Coronary collateral development is an important compensatory mechanism in advanced coronary artery disease, and patients with diabetes mellitus have impaired coronary collateral development. This study tested the hypothesis that statin treatment may increase coronary collateral development in patients with diabetes mellitus. The study population consisted of 149 consecutive diabetic patients who underwent clinically indicated coronary angiography and had >95% stenosis of > or =1 major coronary artery. Clinical information, including age, gender, history of hypertension, smoking, myocardial infarction, clinical presentation, and medications, was recorded before coronary angiography. Coronary collaterals were graded according to the Cohen-Rentrop method. Collateral grading was classified as poor when the collateral grade was 0 to 1 and good when it was 2 to 3. Among 149 patients (85 men; mean age 62 +/- 10 years), 74 (56%) were receiving statin treatment. In multivariate analysis, among demographic, clinical, and angiographic parameters, only statin therapy (odds ratio 3, 95% confidence interval 1.5 to 6.03, p = 0.002) and stable angina pectoris (odds ratio 3.24, 95% confidence interval 1.42 to 7.41, p = 0.005) were found to be independent predictors of better collateral formation. In conclusion, stable angina pectoris and statin treatment are associated with better coronary collateral development in patients with diabetes mellitus.