The activities of glomerular intrinsic antioxidant enzymes (AOEs) were measured in a diabetic spontaneously hypertensive rat (SHR) model. The effects of antihypertensive drugs, i.e. captopril or triple therapy (hydralazine, reserpine, and hydrochlorothiazide), on glomerular intrinsic AOE activities in this model were evaluated. The effects of blood glucose control on the AOE activities were also determined. The aim of the present study was to determine whether activities of glomerular intrinsic AOEs might correlate with disease activity in diabetic SHR. This study showed a decrease of glomerular intrinsic AOE, i.e. Cu/Zn-SOD and Mn-SOD (SOD = superoxide dismutase), glutathione peroxidase, and catalase, activities in diabetic SHR. Glomerular Cu/ Zn-SOD or Mn-SOD, glutathione peroxidase, and catalase activities in non-diabetic SHR were slightly lower than those in nondiabetic WKY rats. These activities in diabetic SHR were significantly improved after captopril or triple therapy or blood glucose control. The levels of urinary albumin excretion, creatinine clearance, and glomerular tuft areas in diabetic SHR were also improved after the therapy. It appears that hypertension and hyperglycemia may influence the glomerular intrinsic AOE activities, albuminuria, creatinine clearance, and glomerular tuft areas in diabetic SHR. Thus, it is indicated that control of blood pressure or blood glucose is a very important factor for preventing renal injuries in the diabetic SHR model.