In type 1 diabetes, the pancreas fails to produce insulin, a hormone that regulates the body's ability to store foods. Type 1 diabetes results in high blood sugar levels that can, over time, lead to complications, such as kidney failure. Controlling blood sugar helps prevent these complications. Blood pressure medications called angiotensin-converting enzyme (ACE) inhibitors can also help prevent diabetes-related kidney failure. It is therefore recommended that patients with diabetes take ACE inhibitors when a protein called albumin appears in the urine (albuminuria), a sign of kidney damage. It is unclear, however, whether patients with even very small amounts of albumin in the urine (microalbuminuria) benefit from ACE inhibitors. Previous studies have shown that ACE inhibitors slow kidney damage, but it is not known whether they can actually restore normal kidney function. Lowering blood pressure can by itself protect kidney function, but it is unclear whether ACE inhibitors protect kidney function in diabetic patients by reducing blood pressure or through some other action.