The platelet aggregation and release reaction, the haemostatic factors and fibrinolytic activity were measured in 36 patients with early retinal vein occlusion (RVO) and 20 control subjects. The mean levels of platelet aggregation, plasma fibronection, factor Ⅷ antigen and plasminogen were significantly higher in the patients than in the controls. These findings showed that the blood hypercoagulant state was present in patients with RVO, and these abnormalities in blood coagulation could play an important role in the onset and development of RVO and its ischaemic complications.