Objective 　To observe the retinal toxicity of repeated intravitreal injection with bevacizumab (Avastin) in diabetic rats. Methods 　Forty male Sprague Dawley (SD) rats were randomly divided into normal group (Group A, 10 rats) and diabetes mellitus group (30 rats). The rats in diabetes mellitus group were induced with streptozotocin injection for diabetic retinopathy model. And then randomly divided into diabetic retinopathy (DR) group (Group B,10 rats), the rats were not intervened; the left eyes of the other 20 rats were intravitreal injected with bevacizumab 3  mu;l (25 mg/ml) for 3 times as experimental group (Group C) ; the right eyes of the 20 rats were not intervened as experimental control group (Group D). 20 days after last intravitreal injection, retinal function was measured by Flicker Electroretinogram (F-ERG);retinal vascular pattern was determined by fluorescence microscopy of ethidium bromide (EB) stained retinal flat mounts; retinal morphological changes were determined by light microscope on hematoxylin-eosin (HE) stained sections;Thy-1 and VEGF expression was measured by immunohistochemistry staining. Results 　F-ERG showed that, the differences of a-and b-waves, the b-wave amplitude and the Ops-wave amplitude in the implicit time between group A, B, C and D were significant (F=33.165, 36.162,19.955, 23.243; P＝0.000); the differences of a-wave amplitude between group A,B,C and D was not significant (F=0.097,P＝0.961). Retinal blood vessel pattern was normal in Group A; retinal vascular vessels were tortuous and irregularly expanded in Group B; retinal vascular vessels of Group C were regular and thinner than Group A; microaneurysm were showed in Group D. Light microscope displayed that the layers of the rat retina of Group A were regular, the retinal architectures of Group B were irregular, the retinal layers were regular in Group C, the retinal layers were irregular in Group D. Immunohistochemistry staining discovered that Thy-1 and VEGF were mainly expressed in ganglion cell layer（GCL）. Conclusion 　Repeated intravitreal injection of bevacizumab is toxic to retina of diabetes mellitus rats.

Citation： ,CHEN Song. Retinal toxicity of repeated intravitreal injection with bevacizumab in diabetic rats. Chinese Journal of Ocular Fundus Diseases, 2011, 27(3): 240-244. doi: Copy