Objective To study the relationship between insulinase activity of erythrocytes(EIA)and diabetic retinopathy(DR)in non insulin dependent diabetes mellitus (NIDDM) patients． Methods EIA,fasting plasma glucose (FPG),fasting plasma insulin (FINS) and glycosylated hemoglobin (HbA1c) were determined in 55 healthy controls,42 NIDDM patients with DR and 44 NIDDM patients without DR． Results EIA was lower,disease duration was longer,and FPG and HbA1c were higher in NIDDA patients with DR.EIA was decreased,duration of NIDDM was lengthened,FPG and HbA1c were increased in NIDDM patients with proliferative DR as compared with NIDDM patients with background DR．The correlation analysis showed,in NIDDM patients with DR,EIA was inversely correlated with FPG,HbA1c and duration of NIDDM． Conclusion Insulinase may play certain role in the onset and development of DR． (Chin J Ocul Fundus Dis,1998,14:132-134)