We evaluated the renal effect of long-term antihypertensive treatment (12 months) with the angiotensin-converting enzyme inhibitor captopril compared to placebo in 15 type 2 diabetic patients with microalbuminuria. The patients were randomly allocated to captopril (n = 9) or placebo (n = 6). After 1-year therapy no significant decrease in blood pressure was demonstrated with captopril (139 ± 17/80 ± 9 versus 138±13/76±6 mmHg) or placebo (138 ± 9/75 ± 6 versus 135 ± 14/79 ±10 mmHg). Only in a small hypertensive subgroup (n = 4) treated with captopril did we find a significant reduction in blood pressure (154 ± 2/88 ± 1 versus 142 ± 7/78 ± 5 mmHg,P < 0.05).="" the="" urinary="" albumin="" excretion="" rate="" did="" not="" change="" significantly="" either="" in="" the="" captopril="" group="" (95.6="" mg/24="" h,="" 25th="" percentile="" 138.4,="" 75th="" percentile="" 25.1;="" versus="" 127.8="" mg/24="" h,="" 25th="" percentile="" 29.3,="" 75th="" percentile="" 222)="" or="" in="" the="" placebo="" group="" (99.2="" mg/24="" h,="" 25th="" percentile="" 58.5,="" 75th="" percentile="" 125.8;="" versus="" 120.9="" mg/24="" h,="" 25th="" percentile="" 62.1,="" 75th="" percentile="" 179.7).="" there="" were="" also="" no="" alterations="" in="" renal="" blood="" flow="" or="" filtration="" rate.="" in="" the="" hypertensive="" subgroup="" treated="" with="" captopril="" a="" reduction="" in="" urinary="" albumin="" excretion="" rate="" after="" 3="" and="" 6="" months="" of="" treatment="" was="" observed="" (captopril="" 73.4="" versus="" 24="" and="" 41="" mg/24="">P < 0.05),="" but="" not="" after="" 12="" months.="" triglyceride="" and="" cholesterol="" levels="" remained="" constant="" before="" and="" after="" treatment="" while="" glycosylated="" hemoglobin="" decreased="" significantly="" after="" 12="" months="" captopril="" (7.8="" ±="" 0.9="" versus="" 6.9="" ±="" 0.7="">P < 0.03).="" we="" conclude="" that="" in="" patients="" with="" type="" 2="" diabetes="" with="" microalbuminuria="" angiotensin-converting="" enzyme="" inhibitors="" may="" have="" protective="" renal="" effects="" in="" so="" far="" as="" a="" lack="" of="" increase="" in="" urinary="" albumin="" excretion="" is="" equivalent="" to="" low="" progression="" in="" renal="">