Determination of fibrinolytic activity of male adnexal f l uid (human seminal fluid, dog prostatic fluid) was made using fibrin-plate method. The results are summarized as follows. I. Fibrinolytic enzymes of human seminal plasma. 1) In very few instances, a little plasmin ac t ivity was found in human seminal plasma which was proved to be almost all plasminogen activator and so proactivator was absent or trace. 2) As thermostability, the fibrinolytic activity showed a peak at 37°C in a range between pH 4 and 9. 3) There was n o significant relationship between fibrinolytic activity and number or motility rate of spermatozoa in patients with male sterility. 4) In patients with male sterility, fibrinolytic activ i t y was increased in all cases after treatment with gonadotropin and testosterone. However the activity showed a decrease around 40 th. to 60 th. day of treatment in many cases. More than a half of cases, moreover, the activity again increased at 20 days after cessation of the treatment. II. Fibrinolytic enzymes of dog prostatic fluid. 1) Fibrinolytic activity of prostatic fluid obtained from so called Huggins' dog was determined. 2) Fibrinolytic activity of dog prostatic fluid showed highest peak during 20 to 40 minutes followed by a decrease around 120 minutes. 3) As the increase in dose of pilocarpin-H CI injected, the amount of prostatic fluid and activity of fibrinolysis were increased. 4) Treatment with various h o rmones made the fibrinolytic activity of prostatic fluid altered. Increase of fibrinolytic activity was achieved after testosterone propionate or gonadotropin injections, slight in crease was observed after ACTH, anabolic hormones or prolactin injections, slight decrease after cortisone therapy and decrease after estrogen administration. No significant change occurred after treatment with thyroid hormone or antithyroid agents.