Objective To investigate the effect of topical treatment with antisense oligonucleotides（ASON）targeting tumor necrosis factor-alpha;（TNF-alpha;）on the pathological process of experimental herpes simplex virus type-Ⅰ（HSV-Ⅰ）induced chorioretinitis in mouse eye. Methods Fifty BALB/c mice were randomly divided into experimental and control group（twenty five mice in each group）.HSV chorioretinitis model was induced in each mouse by inoculating 1times;105 plaque-forming units （pfu） of HSV-Ⅰ（KOS strain）into anterior chamber of the right eye.In experimental group，Fluorescein isothiocyanate （FITC）-labeled ASON targeting TNF-alpha; 2 mu;l were injected sub-conjunctiva in the left eye1day before and 1 and 4 days after the infection;while phosphate buffer solution was injected in the same way in control group.The inflammation changes of the eyes in the 2 groups were observed and the clinical grades were assessed according to the extends of anterior-chamber inflammation，vasodilatation of cornea and iris，formation of cataract，and vitreous opacity. All of the mice were executed 10 days after the infection and were observed histologically. The contents of TNF-alpha; in retina and choroid were measured by enzyme-linked immunobsorbent assay（ELISA）. Results After the infection，acute inflammation appeared in the right eyes in both groups. The inflammation of the left eyes in experimental group was significantly milder than which in the control group.Twelve left eyes had necrotic chorioretinitis in different degrees in the control group while 2 left eyes had mild chorioretinitis in the experimental group. The difference of the number of inflammatory cells between the 2 groups was statistically significant in retina，choroid，and ciliary body（P＜0.05）and was not obvious in anterior chamber，vitreous cavity，and iris（P＞0.05）.The content of TNF-alpha; in choroid and retina was（60plusmn;1.25）pg in the experimental group and（305plusmn;1.03）pg in the control group（P＜0.05）. Conclusions TNF-alpha; ASON treating HSV-Ⅰinduced chorioretinitis may reduce the content of TNF-alpha; in affected mice eyes and decrease the inflammatory reaction. (Chin J Ocul Fundus Dis, 2006, 22: 245-248)