·AIM:To investigate the cause of vitreous hemorrhage and constitutional characteristics.·METHODS:The clinical data of 218 eyes of 193 patients with vitreous hemorrhage were studied for the causal analysis from August 2002 to February 2007.·RESULTS:Of all the causes,proliferative diabetic retinopathy(PDR)was the principal cause(72 patients,37.3%),the second was ocular trauma(47 patients,24.4%),the third was retinal vein occlusion(RVO,36 patients,18.7%),followed by rhegmatogenous retinal detachment(10 patients,5.2%)and Eales’s disease(9 patients,4.7%).Compared to the distribution of minority,nationality and Han nation,there were no statistical differences between them(χ2=15.648,P=0.239).67 cases in youth group(<45 years old),the principal cause was ocular trauma(37 patients,55.2%),the second was PDR(12 patients,17.9%),the third was Eales’s disease(9 patients,13.4%).56 cases in middle-aged group(45-59 years old),PDR was the principal cause(28 patients,50.0%),the second was RVO(14 patients,25.0%),followed by ocular trauma(7 patients,12.5%).70 cases in old group(≥60 years old),the principal cause was PDR(32 patients,45.7%),the second was RVO(21 patients,30.0%),followed by exudative age related macular degeneration(5 patients,7.1%).There was statistically significant difference among them(χ2=115.154,P<0.01).The major causes of 124 males were ocular trauma,PDR,RVO and Eales’s disease,accounted for 34.7%,32.3%,13.7%,5.7%,respectively.The principal causes of 69 females were PDR,RVO,ocular trauma and rhegmatogen-ous retinal detachment,accounted for 46.4%,27.5%,5.8%,4.4%,respectively.There was statistically signifi-cant difference between them(χ2=36.095,P<0.01).·CONCLUSION:Ocular trauma、PDR and Eales’s disease are the main causes of the vitreous hemorrhage in youth group.PDR,RVO,ocular trauma are the main causes of the vitreous hemorrhage in middle-aged group.PDR,RVO and exudative age related macular degeneration are the main causes in old group.The major causes of males are ocular trauma,PDR,RVO and Eales’s disease.The principal causes of females are PDR,RVO,ocular trauma and rhegmatogenous retinal detachment,PDR and Eales’s disease are the major causes of bilateral vitreous hemorrh-age.The fundus neovascular cracking and bleeding and traction retinal detachment are the inherent causes.·