A 63-year-old man was evaluated for a lifelong history of bleeding commencing with frequent epistaxis as a child; all previous routine coagulation parameters were within the normal range. The patient's hemorrhagic disorder is characterized predominantly by delayed bleeding at surgical sites. In the resting state, there was no clinical or laboratory evidence of excessive fibrin(ogen)olysis. Bleeding was not caused by disseminated intravascular coagulation, factor XIII deficiency, alpha 2-antiplasmin deficiency, or dysfibrinogenemia. It was found that the patient was deficient in plasma PAI-1 antigen and activity but with approximately half normal antigen and normal activity of platelet PAI-1. The low concentration of plasma PAI-1 was insufficient to neutralize circulating t-PA, resulting in high t-PA activity with normal antigen and causing the hyperfibrinolytic activity observed. Studies on seven family members of the proband indicated autosomal inheritance of plasma PAI-1 deficiency. Studies on this patient emphasize a clear correlation between decreased plasma PAI-1 activity and hyperfibrinolytic bleeding and also emphasize the unique role of plasma PAI-1 in the balance between the coagulation and fibrinolytic mechanisms.