Objective To investigate the relationship between expression of retinal intercellular adhesion molecule-1 (ICAM-1) and blood-retinal barrier (BRB) rupture and therapeutic effect of intravitreous injection with triamcinolone acetonide (TA) on blood-retinal barrier rupture in rats with diabetes mellitus (DM). Methods Diabetic model of Wistar rats was induced and were divided into normal control group, DM-4-month group and DM-6-month group. Each group was subdivided into immunohistochemcial staining and BRB measurement groups. BRB measurement group was further divided into non-TA treatment group, 1-week-TA treatment group, and 2-week-TA treatment group. The rats were intravitreously injected with 5 mu;l TA. The digested retinal preparation was stained by immunohistochemcial method to observe the expression of retinal ICAM-1 and morphological changes. The mean optic density (A) value of endothelial cells was measured by image-analyzing software to quantify the expression of ICAM-1. BRB changes were measured by content test of retinal Evans blue (EB). Results In the immunohistochemcial staining groups, there was no significant positive expression of ICAM-1 in retinal capillary in control group. Compared with the control, there was significant positive expression of ICAM-1 in DM-4-month group (P＜0.001) with some morphological changes such as irregular width of capillary caliber, and there was enhanced positive expression of ICAM-1 in DM-6-month group (P＜0.001) with aggravated morphological changes and even acellular capillary. In the BRB measurement groups, there was no significant difference of EB content(P＞0.05) among control groups. The EB content in two DM groups significantly increased compared with that in the controls (Plt;0.001), and higher in DM-6-month group than that in DM-4-month group (Plt;0.01). In TA treatment groups, the EB content in all the DM groups significantly decreased (Plt;0.001) but with no significant difference among the groups(P＞0.05). EB content in DM-4-month group after 2-week treatment almost reached to normal value (P＞0.05) while was higher in the rest of TA treatment groups than that in the control group (Plt;0.05). Rectilinear correlation between A value of endothelial cells and the retinal EB content(r=－0.959)was found. Conclusion There is a positive relation between the expression of ICAM-1 and BRB rupture in retina of DM rats, and intravitreous injection with TA can effectively alleviate BRB rupture. (Chin J Ocul Fundus Dis, 2006, 22: 24-27)