Method: In a double-blind, cross over study, 24 patients with diabetic nephropathy who were already receiving either ACE inhibitor(lisinopril 20-40 mg/day ) or ARB( losartan 25-100 mg/day )were given spironolactone( 25 mg during the first month and 50 mg during the second and third month if serum K remained ok) or matching placebo with 1 month of washout in between. All patients were from a single center and exclusively male veterans. Blood pressure, serum creatinine, serum K and spot urine protein/creatinine were measured at the beginning and end of each study period. The study was started in May of 2003 and completed in May 2006.