The clearance of radiolabeled human fibrinogen fragments X and Y was studied in the mouse model. Fragment X cleared rapidly from the circulation with less than 10% of the ligand remaining in the circulation at 4 hr. The clearance of fragment Y was somewhat slower, but was identical to the rate of clearance of fragment D1. Competition studies indicated that fragments X, Y, D1 amd D1 dimer clear via the same, saturable pathway. Fragment E did not compete for the clearance of there ligands. Tissue distribution studies demonstrated that the liver was the principle site of clearance of all three ligands. The kidneys also cleared a fraction of each ligand in the order fragment D3 greater than D2 greater than D1 greater than Y greater than X. This pattern suggests that renal clearance is a passive phenomenon dependent on the size of the fibrinogen degradation product.