Twentyfour patients with various forms of renal diseases were treated with urokinase (U.K.). Of these patients, twelve had chronic glomerulonephritis (G.N.), three had membranoproliferative G. N., two had rapidly progressive G. N., one had membranous nephropathy and six had chronic renal failure. Daily dosis of U.K. was 6000 internatinal units. Laboratory data listed below were compared before and after U.K. treatment; urinary output (U.V.), urinary protein (U-P), urinary erythrocyte (U-RBC), blood pressure (B.P.), blood urea nitrogen (BUN), serum creatinine (Scr), creatinine clearance (Ccr), fibrin/fibrinogen degradation products in urine and in blood (U-FDP, B-FDP) and serial renal biopsies. These patients divided into two groups depend on effectiveness of U.K. treatment. Ten of these were responded well, however others were not. In regard to t.ne clinical course, rapid progression or acute exacerbation was found just before treatment in all cases of effective group (Group I) as compared with five cases of not effective group (Group II). The mean period from rapid progression or acute exacerbation to start the therapy was 2.6±1. 3 months (M.) in Group I and 6.3±1.6 M. in another. All patients in Group I had histologicaly marked proliferation, crescents formation and less frequently fibrin thorombi. Immunof luorescent study of these revealed deposition of fibrin/fibrinogen and positive immunoglobulins and complements. In Group I, the administration of U.K. was associated with statistically significant improvement of U.V., U-RBC, BUN, Ccr and B-FDP and remarkably improvement of B.P., Scr, U-FDP and serial renal biopsy findings. But U-P was increased except three cases in Group I. <BR>The indication of fibrinolytic therapy with U.K. was thought to be as follows ; 1) rapid progression or acute exacerbation in clinical course, 2) rapid deteriolation of renal function, rapid increase of BUN, B.P. and U-RBC and continuous abnormality of U-FDP in laboratory examination and 3) diffuse prolif erative G. N. with crescents formation and/or fibrin thorombi and glomerular deposition of fibrin or fibrinoid material in renal biopsy findings. The time of start to therapy was thought to be suitable within three M. from acute exacerbation or rapid progression. The criteria of effect was able to be judged as follows ; 1) serial renal biopsy findings and serial renal function tests in absolute condition, 2) Scr, U-RBC and B.P. in relative condition and 3) BUN, U.V., U-P and U-FDP in additional condition. According to the criteria, all the patients of Group I are possible to be judged effectively and all of Group II to be judged not effectively. The fibrinolytic therapy is effectively as same as anticoagulant therapy in G.N., if the patient will be selected well.