1. The time sequence of glomerular fibrin deposition, renal cortical fibrinolytic response and thrombocytopenia after thromboplastin infusion in rats has been established. 2. Fibrin clearance is rapid and is associated with markedly increased cortical fibrinolytic activity. 3. Plasma fibrinolytic activity was unchanged. 4. Experiments in which the dose-response relationship between thromboplastin dose, fibrin deposition and fibrinolytic response was examined showed that fibrinolytic response increased with fibrin deposition in glomeruli. 5. The dose—response experiments also provided data which suggested that the method of measurement of cortical fibrinolytic activity in the presence of deposited fibrin measures excess rather than total plasminogen activator production.