The intraglomerular location of coagulation-fibrinolysis factors (CFF) and a platelet membrane antigen (glycoprotein IIb-IIIa; GPIIb-IIIa) was determined in 101 patients with various glomerular diseases. Renal biopsy specimens were examined by immunofluorescence microscopy, using antisera against fibrinogen/fibrin reactive antigen (FRA), cross-linked fibrin degradation products (XL-FDP), fibronectin (FN), factor XIH-subunit a (F-XIIIa), plasminogen (Pig), α<sub>2</sub>-plasmin inhibitor (α<sub>2</sub>-PI) and GPIIb-IIIa. Intraglomerular deposits of the CFF were found at high rates in patients with IgA glomerulonephritis (GN), membranous nephropathy (MN) and lupus GN. The coexistence of deposits of these factors was ascertained by the double-staining method. The deposition rates of XL-FDP and GPIIb-IIIa were very low in patients with minimal-change nephrotic syndrome and focal glomerulosclerosis. Some cases of diabetic glomerulosclerosis (DGS) showed CFF deposition. FRA deposits associated with F-XIIIa and FN may indicate the presence of the cross-linked fibrin. Furthermore, the presence of Pig deposits together with α<sub>2</sub>-PI and XL-FDP suggests the deposition of fibrin followed by fibrinolysis, but not of fibrinogen, and the coexistence of GPIIb-IIIa suggests the involvement of platelets in the reactions. These studies provide evidence that stabilized fibrin deposition with subsequent fibrinolysis and platelet activation take place in glomeruli in a fairly large proportion of patients with IgA GN, MN and lupus GN and in some cases of DGS.