The prevalence of RAAS in non-insulin-dependent diabetic patients ranges from 17 to 44%. The prevalence increases exponentially in the presence of several risk factors such as severe arterial hypertension, severe renal insufficiency, macroangiopathy, smoking, and insulin requirement. In diabetic patients, RAAS should be investigated in patients with severe arterial hypertension, repeated pulmonary oedemas, and renal insufficiency without any clear etiology associated with a mild proteinuria and/or with a renal insufficiency secondary to the administration of angiotensin converting enzyme inhibitors or angiotensin II receptors antagonists. Asymmetrical size of the kidneys should also prompt the physician with a suspicion of RAAS. There are several specific criteria, that may confirm the suspicion of a RAAS. Renal arteriography is still the goal standard for diagnosing renal artery stenosis.