Objective To observe in vitro the protective effect of cranial nerve growthine (CNG) on the optic nerve injured by acute ocular hypertension. Methods Thirty white rabbits were divided into five groups,and 6 in each.The acute ocular hypertension(50 mm Hg) models were established by forcing perfusion of normal saline solution into the anterior chamber sustained for 6 h in one eye,and the contral ateral eye of each rabbit was regard as control.Three rabbits in each group were then treated by CNG 0.2 ml intramuscularly every day.The optic nerve and retina was surgically removed at five different time points (lst,3rd,7th,15th and 30th day) after operation.With the HRP orthograde tracing technique and transmitted electron microscope,the effect of CNG on the optic nerve was observed by the changes of axonal transport and ultrastructure of optic nerve. Results Compare with experimental control groups (25.17plusmn;1.03),HRP reactive products of treated groups (39.79plusmn;2.29) markedly increased after seven days (Plt;0.01).The degeneration of axons in treated groups was relatively lighter after fifteen days and some axons recovered after thirty days. Conclusion CNG might improve the axonal transport and the recovery of axons after the optic nerve injured by acute ocular hypertension. (Chin J Ocul Fundus Dis,2000,16:88-90)