Fibrin plate assays revealed that human burn blister fluid represses plasmin-induced fibrinolysis. While this repression is significant, it is not as potent as that of human serum. Ibuprofen, a nonsteroidal anti-inflammatory drug, antagonizes blister fluid inhibition of fibrinolysis. The activity of ibuprofen appears to be unrelated to the synthesis of prostaglandins because other nonsteroidal drugs that were tested, such as indomethacin, imidazole, and tolmetin had significantly less antagonistic activity. This plasmin inhibition, which is contained in burn blister fluid, may contribute to vascular occlusion after burn injury, which leads to secondary dermal ischemia and necrosis in patients traumatized by burns.