Hypertension and diabetes co-exist more commonly than would be expected from their individual prevalences. Elevated blood pressure is most commonly due to coexisting essential hypertension, or diabetic renal disease. Early stages of diabetic renal disease can be identified by detecting microalbuminuria. Standard measures of blood pressure are not necessarily raised, but 24-hour ambulatory measures frequently identify a loss of nocturnal drop in blood pressure. Treating hypertension aggressively is important in slowing the inexorable decline in glomerular filtration rate. In diabetes there appears to be no 'J'-shaped relationship between blood pressure and cardiovascular events, thus removing any concern about attaining low blood pressures as long as the patient is asymptomatic. Morbidity and mortality in these patients is usually associated with cardiovascular events, and it is important to assess the effect of drugs on left ventricular hypertrophy and metabolic parameters. Many drugs are effective at lowering blood pressure, but angiotensin-converting enzyme inhibitors may have an additional renoprotective action. alpha-Adrenergic antagonists may improve lipid profiles and calcium antagonists are probably lipid neutral, making these drugs useful alternatives. Dihydropyridine calcium antagonists (eg, nifedipine) may augment protein-uria, and hence non-dihydropyridine calcium antagonists (eg, verapamil, diltiazem) would be preferred. beta-Blockers and thiazide diuretics have the disadvantage of causing a deterioration in glycaemic and lipid profiles, but can be useful on occasions.