Purpose:To investigate the relationship between the diabetic retinopathy (DR) and the activity of plasma tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI).Methods :tPA and PAI activities were measured by chromatogenous substrate assay in plasma samples obtained from patients with and without diabetic retinopathy (n = 42). Retinopathy was determined by stereoscopic color fundus photographs graded according to a modification of Chinese National Fundus Disease Academic Meeting. And 21 sex-age matched normal people were as controls. This study was in a masked fashion.Results:①tPA activity was lower and PAI activity was higher in all of diabetic patients than those in controls (P<0. 001); ②tPA activity was lower and PAI activity was higher in proliferative DR (PDR) subgroup than those in non-DR (NDR) and background-DR (BDR) subgroups (P<0.01,respectively); ③there was no significant difference between BDR and NDR subgroups (P>0. 05); and ④the results also suggested that the seve Purpose: To investigate the relationship between the diabetic retinopathy (DR) and the activity of plasma tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI). Methods: tPA and PAI activities were measured by chromatogenous substrate assay in plasma samples obtained from patients with and without diabetic retinopathy (n = 42). Retinopathy was determined by stereoscopic color fundus photographs graded according to a modification of Chinese National Fundus Disease Academic Meeting. And 21 sex-age matched normal people were as controls. This study was in a masked Results: ①tPA activity was lower and PAI activity was higher in all of diabetic patients than those in controls (P <0.001); ②tPA activity was lower and PAI activity was higher in proliferative DR (PDR) subgroup than those in non (P <0.01, respectively); ③ there was no significant difference between BDR and NDR subgroups (P> 0.05); and ④ the results also s uggested that the seve