To determine whether inherent fibrinolytic differences may exist in racial groups (black americans, BA vs. white americans, WA), 55 different individual racially-derived human umbilical vein endothelial cell (HUVEC) cultures (35 BA and 20 WA) were analyzed in terms of their fibrinolytic protein (t-PA, u-PA and PAI-1) antigen and mRNA levels. Values (mean ± SD) for measured fibrinolytic component levels include: cell-associated t-PA antigen (ELISA), 1.14 ± 0.82 ng/ml8.6 10 5 cells/24 hr in BA and 0.70 ± 0.85 ng/ml in WA (p=0.0624); secreted t-PA antigen, 18.65 ± 17.06 ng/ml in BA and 10.37 ± 6.38 ng/ml in WA (p=0.0422); t-PA/cyclophilin mRNA ratios (Northern blot analysis), 1.90 ± 1.34 in BA and 1.32 ± 0.70 in WA (p=0.0776); cell-associated PAI-1 antigen, 71.10 ±30.16 ng/ml8.6 10 5 cells/24 hr in BA and 108.85 ± 56.89 ng/ml in WA (p=0.0022); secreted PAI-1 antigen, 1,582.13 ± 612.67 ng/ml in BA and 1,992.17 ± 711.50 ng/ml in WA (p=0.0285); 2.4 kb PAI-1/cyclophilin mRNA ratios, 0.59 ± 0.39 in BA and 0.79 ± 0.31 in WA (p=0.1085); 3.4 kb PAI-1/cyclophilin mRNA ratios, 0.70 ± 0.47 in BA and 0.77 ± 0.54 in WA (p=0.6322). These combined data suggest that cultured HUVECs from BA express significantly higher levels of t-PA, lower levels of PAI-1 and ∼1.72-fold lower molar ratio of PAI-1/t-PA antigen (183.99 ± 168.81 vs. 315.92 ± 164.99) (p<0.05) than cultured HUVECs from WA, presumably reflecting an apparent inherent increased fibrinolytic potential in cultured HUVEC derived from BA.