Objective To investigate the effects of intravitreal injection of matrix metalloproteinase-3 (MMP-3) on the vitreoretinal adhesion and the vitreous gelatin. Methods Twenty-four pigmented rabbits were randomly divided into 3 experimental groups（group A, B, and C）and one control group with 6 rabbits (12 eyes) in each. Different concentrations of 0.1 ml MMP-3 (5,10, 20 ng in group A, B, and C, respectively) and equivalent dose of balanced salt solution were intravitreally injected to the rabbits, respectively. Clinical examinations (such as gross observation, slit-lamp biomicroscopy, indirect fundus ophthalmoscopy ), electroretinography (ERG) and fundus fluorecein angiography (FFA) were taken before and after injection. Results One week after injection, posterior vitreous detachment (PVD) and focal vitreous liquefaction were recognized clinically for the first time in 1 eye in group B. By the end of this study, clinically detected PVD developed in 1 eye in group A, 3 eyes in group B, but the synchisis developed slowly, and no liquefaction or PVD occurred in control group. As for the histological examination, partial PVD was observed in 1 eye in group A and 3 eyes in group B 60 minutes after injection. All of the eyes in group A and B showed partial PVD 1 week after injection, and the area of PVD enlarged in contrast with before. Complete PVD were recognized in 1 eye in group A and 3 eyes in group B 15 weeks after injection, and the cleavage was narrow and limited. In group C, inflammatory cell infiltration in the inner layer of retina, destruction of retinal structure, and fluorescein leakage at late phase was found in the early period after injection. Conclusions MMP-3 is effective in disrupting the adhesion of the posterior hyaloid to the inner limiting membrane leading to PVD, and helpful to some extent in producing vitreous liquefaction. The dose of 10 ng MMP-3 is safe and effective for the rabbits eyes, which may be used as an promising assistant of vitreous surgery. (Chin J Ocul Fundus Dis，2004，20：67-132)