Aim To evaluate the protective effect of irbesartan on renal function in elderly patients with microalbuminuria.Methods 113 old patients with microalbuminuria,who were suffered from hypertension or diabetes,were involved in the study.Patients were divided into two groups,irbesartan group or control group,all received strictly antihypertensive therapy with irbesartan or without any angiotensin-converting enzyme inhibitor(ACEI) or angiotensin receptor blocker(ARB).Results The average levels of systolic blood pressure and diastolic blood pressure in two groups decreased significantly compared with baseline levels(P<0.05).But,the levels of blood pressure had little difference between the two groups(P>0.05).Urinary α1-microglobulin and urine microalbumin in irbesartan group after treated for 12 months were significantly decreased from 18.4±6.5 mg/L to 13.5±4.2 mg/L and from 78.3±12.7 mg/L to 58.4±9.3 mg/L,respectively(P<0.05).Meanwhile,there was no such a change in control group.The serum creatinine and glomerular filtration rate changed slightly after treatment for 12 months in two groups.Conclusion Irbesartan is beneficial to reduce urinary albumin and to protect renal function in elderly patients,who suffered from hypertension or diabetes mellitus.