This study was conducted on type 2 non-insulin-dependent diabetes mellitus (NIDDM) cases and healthy blood donors. Lipid peroxidation (LP) products in plasma and red blood cell (RBC) hemolysates were estimated as total thiobarbituric acid reactive substances (TTBARS). The plasma and hemolysate reduced and oxidized glutathione (GSH and GSSG) levels are compared. In the hemolysates the antioxidant enzymes namely superoxide dismutase (SOD), glutathione peroxidase (GPx-ase), glutathione reductase (GR-ase) and catalase (C-ase) are also compared. The RBC filtration characteristics are determined and compared with controls: 1. LP and GSH in diabetic plasma were significantly higher, but in the hemolysate the GSH raised but the LP was significantly lower in diabetics than in healthy controls. 2. Superoxide dismutase and C-ase were significantly higher in NIDDM hemolysate. Contrary the GPx-ase activity was significantly lower in diabetics. 3. The diabetic RBCs filtration characteristics are changed in respects significantly namely the Fi was lower, the Tc and CR were higher. It means higher rigidity and oxidative damage of the membrane of diabetic RBCs.