Objective To observe apoptotic and proliferative characteristics of the retinal vascular end othelial cells (RVECs) of the 1～16 weeks diabetic rats and p53 and bcl-2 expressions of the rats,in order to probe the pathogenic mechanism of diabetic retinopathy(DR). Methods Models of diabetic Wistar rats were made by alloxan venous injection.The retinal blood vessels were filled by ink,the wholemounts and paraffin-embedded sections of the retinas were made,TUNEL staining and Immunohistochemical ABC staining were used,and light microscopy was taken,in succession. Results Apoptosis of the RVECs was not found.Compared with control group,the morphologic features of the RVECs and the structure of the retinal blood vessels remained unchanged.In the period from the 10th to the 16th week,the immunohistochemical stain of PCNA,BrdU,p53,and bcl-2 for RVECs revealed positive results,but there was no any sign of the RVECs stacking and proliferating or new blood vessels forming in the retinas.In control group,the reaction of immunological stain of the aforementioned parameters was negative. Conclusions No accelerated apoptosis and proliferation of the RVECs in the 1～16 week diabetic rats happen after alloxan injection.Almost all of the RVECs were stimulated to enter the cell cycle in the 10th week.Expression of p53 and bcl-2 might play an important role in stabilizing the RVECs in early stage of diabetes. (Chin J Ocul Fundus Dis, 1999, 15: 157-159)