The erythrocytic membrane ATPase activity and intraerythrocytic cation levels have been measured in 20 noninsulin dependent diabetes mellitus(NIDDM)patients with retinopathy(DR group),20 NIDDM patients without retinopathy(DM group)and 20 normal subjects (C group)respectively.The activities of Na+- K+-ATPase and Ca2+-ATPase were significantly lower in both DR and DM groups than in C group.The levels of intraerythrocyte sodium and calcium were significantly higher,and of magnisium waws significantly lower in DR and DM groups than in C group.The above observed abnormalities especially decreased level of magnisium,were more significant in DR group than in DM group. （Chin J Ocul Fundus Dis,1994,10:11-13）