According to the W.H.O. criteria (160/95 mmHg), arterial hypertension is present in about one third of diabetic patients. But the W.H.O. criteria are not appropriate in insulin-dependent diabetics. There is increasing evidence that a slight increase of blood pressure values may have a deleterious effect on various localizations of diabetic angiopathy. Arterial blood pressure is a major predictive factor for stroke or death due to coronary heart disease. The incidence and prevalence of diabetic retinopathy are significantly correlated with systolic and/or diastolic blood pressure values. In patients with incipient diabetic nephropathy, a slight elevation of blood pressure values is usually observed, an antihypertensive treatment may reduce albumin excretion rate and may prevent clinical diabetic nephropathy. Antihypertensive treatment is the more effective and the best tolerated of all interventions dedicated to reduce albumin excretion. Calcium antagonists and angiotensin converting enzyme inhibitors are at the present time the drugs to be used in the treatment of hypertensive diabetic patients as they are more effective and better tolerated than the usual antihypertensive agents. A part from their antihypertensive effect, they also improve cardiac, cerebral and intra-renal haemodynamics.