Cardiovascular complications are frequently present in insulin-dependent (IDDM) and non-insulin dependent diabetes mellitus (NIDDM) patients and confer a very poor prognosis. In this overview we critically analyse the current literature with regard to the benefits and also the possible harms of the available pharmacological treatment strategies in these patients. To date, insulin is the only hypoglycaemic agent which has been proven both effective and safe in NIDDM patients with cardiovascular complications. Also, several trials indicate that treatment with oral hypoglycaemic agents may confer a substantial risk in such patients. Conventional antihypertensive treatment, including betablockers and diuretics, has been convincingly shown to reduce mortality and morbidity in diabetic nephropathy and in NIDDM patients. However, this may not be the case with newer antihypertensive agents, such as angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers. Likewise, convincing evidence is lacking that these newer antihypertensive agents provide meaningful clinical benefit when compared to the conventional treatment regarding slower progression of diabetic nephropathy or their impact on lipid and glucose metabolism. Cholesterol lowering therapy with statins and aspirin treatment have also been repeatedly shown to improve the prognosis of diabetic patients with coronary heart disease.