The subjects in this study were 50 healthy controls (age .18 yrs), recruited from the hospital or research centre staff, with no history of kidney disease, hypertension, or diabetes, and 100 renal transplant recipients from The Ottawa Hospital Renal Transplant Program, age .18 yrs, and .3 months posttransplant. At the time of enrollment, half of the transplant subjects (n = 50) were also enrolled in an ongoing randomized controlled trial to determine the effect of the ACE inhibitor ramipril on transplant outcomes (ACE inhibition for the preservation of renal function and survival in kidney transplantation; International Standard Randomized Controlled Trial Number Registry ISRCTN-78129473), but had not yet received either placebo or ramipril. These subjects had documented significant proteinuria (.200 mg urinary protein/day) at baseline. The 50 other transplant recipients were patients without significant proteinuria (spot urine ACR in the normal range, or ,200 mg proteinuria/day). Subjects were excluded if they were taking ACE inhibitors, angiotensin receptor antagonists, or renin inhibitors, or if they were pregnant or currently had a urinary tract infection.