Résumé : The gel filtration of a fraction prepared by precipitation of a crude extract of human benign hyperplastic prostate tissue resulted in two separated peaks of direct proteolytic activity (DPA1 and DPA2) devoid of any kinase or plasminogen activator activity. A third peak showing proteolytic inhibitory activity (PIf) was also obtained. DPA1 was active on fibrinogen as well as on casein, although the proteolysis of fibrinogen was limited as shown by the electrophoretic pattern of breakdown products. This peak had an esterase activity on p-tosyl-Larginine methyl ester (TAME) but not on L-lysine methyl ester (LME). DPA2 was devoid of esterase activity and was much more active on fibrinogen than on casein, releasing large fragments of fibrinogen. DPA1 and DPA2 appeared to be different from plasmin, to have an active serine center and not to be dependent on thiol groups for their activity. Their possible role in the pathogenesis of the hemorrhagic diathesis associated with some prostatic disorders should be envisaged. Although the human prostate crude extract contained an antiplasmin and an antitrypsin activity, PIf was ineffective against plasmin and did not inhibit either one of the two DPA's. PIf had identical antigenic determinants as plasma α1-antitrypsin. © 1976.