Activities of plasminogen activators (PA) and their inhibitors were studied in the bullous lesions of 2 siblings with recessive dystrophic epidermolysis bullosa (RDEB). The hematological findings of the patients revealed hyperfibrinogenemia, hyper-gamma-globulinemia and marked thrombocytosis. The immunofluorescent studies showed strong deposits of plasminogen, fibrin-degenerative products and alpha 1-antitrypsin around the blister lesions. On the other hand, alpha 2-macroglobulin (alpha 2-M) was sparsely deposited. The levels of alpha 2-M in the blister fluid of the patients were also decreased in comparison with those from patients with other bullous dermatoses. The topical application of antibiotic ointment with strong PA inhibitor was clinically effective when applied to the blister and eroded lesions of the patients. These findings suggest that the increased activity of PA may play an important role in the development of blister formation in patients with RDEB.