OBJECTIVE: To assess whether the extent of primary and secondary coronary heart disease (CHD) prevention in older British men and women differs between patients with and without diabetes. DESIGN: Two prospective cardiovascular cohort studies. SETTING: 24 British towns. PATIENTS: 4252 men and 4286 women aged 60-79 years examined between 1998 and 2001. MAIN OUTCOME MEASURES: Use of aspirin, statin, and blood pressure lowering treatment and risk factor control, examined by diabetic status and history of established CHD. RESULTS: About 20% of the men and 12% of the women had established CHD at age 60-79 years and 7% of the men and 5% of the women had diabetes. In primary CHD prevention, patients with diabetes were more likely to receive CHD risk reducing medications than those without diabetes, but the proportions receiving preventive treatments in both groups were low. In secondary prevention, diabetic and non-diabetic patients received similar levels of treatment, with the exception of angiotensin converting enzyme inhibitors and (for women only) blood pressure lowering treatment, which were more widely used among diabetic patients. There were no clear differences in blood pressure control or cigarette smoking by diabetic status in primary or secondary prevention. Mean total cholesterol concentrations were lower in diabetic patients independently of treatment with statins. CONCLUSIONS: Despite their exceptionally high CHD risk, many opportunities to reduce CHD risk among patients with diabetes have not been taken.