A randomized, prospective, clinical trial has been initiated to continue follow-up in a subset of the patients previously enrolled in the recently completed Study of Angiotensin-Converting Enzyme Inhibition (ACEi) in Type 1 Diabetic Nephropathy. In that study, the use of captopril was associated with a 48% reduction in the risk of doubling the serum creatinine and a 50% reduction in the risk of experiencing dialysis, transplantation, or death, compared with the use of placebo. These effects were independent of captopril's effect on the blood pressure. This study is designed to determine whether the level of mean arterial blood pressure (MAP), using the ACE inhibitor ramipril as the primary therapy, is associated with an improved prognosis of diabetic nephropathy with respect to (1) the rate of decline in renal function; (2) the rate of progression to end-stage renal failure; (3) the clinical course of proteinuria; (4) morbidity; and (5) mortality. Patients are randomized into one of two distinct blood pressure control groups, an Intensive Group #1, MAP < or = 92 mm Hg; and a Moderate Group #2, MAP 100 to 107 mm Hg. Patients previously enrolled in the "Study of ACEi in Type 1 Diabetic Nephropathy" whose serum creatinine was less than 4.0 mg/dL (354 mumol/L) were eligible for randomization into this study. All patients will receive ramipril (2.5 to 10.0 mg/day) as the primary therapy, with the addition or removal of other antihypertensive agents as needed to achieve the assigned blood pressure goal.(ABSTRACT TRUNCATED AT 250 WORDS)