OBJECTIVE: ACE inhibitors delay the progression from incipient to overt diabetic nephropathy and reduce albumin excretion rate (AER), independently of blood pressure. Angiotensin II type 1 receptor antagonists produce similar effects on microalbuminuria and mean arterial pressure. The aim of this study was to evaluate the effect of irbesartan on microalbuminuria and blood pressure in hypertensive and normotensive type 2 diabetic patients. RESEARCH DESIGN AND METHODS: Sixty-four microalbuminuric hypertensive (group 1) and 60 microalbuminuric normotensive (group 2) type 2 diabetic male patients, matched for age, BMI, HbA(1c), and diabetes duration, were enrolled. Each group was divided into two subgroups receiving either irbesartan (150 mg b.i.d. orally) or placebo for 60 days. After 15 days of washout, irbesartan was given to the subgroups who had received the placebo, and vice versa, in a randomized double-blind crossover study. RESULTS: In microalbuminuric hypertensive type 2 diabetic subjects, irbesartan reduced 24-h mean systolic and diastolic pressure and AER. In microalbuminuric normotensive type 2 diabetic patients, irbesartan reduced AER. CONCLUSIONS: These results indicate the beneficial effects of irbesartan on AER in type 2 diabetic subjects, independently of its antihypertensive effects.