The role of N-linked carbohydrate chains, bound to the polypeptide chains Bβ and γ of fibrinogen, in the process of fibrin gel formation has not been understood well yet, although it has been well known that the deglycosylation accelerates the fibrin polymerization. We investigated the time course of the fibrin polymerization employing the turbidity and light scattering measurements focusing on the role of carbohydrate chains. Deglycosylated bovine fibrinogen was prepared by using peptide N-glycosidase F, PNGF, and the effects of its mixing with the intact one were examined. Fibrinopeptide release and protofibril growth were not affected by the deglycosylation at all. However, only a slight mixing of deglycosylated fibrinogen by 5 and 10 % resulted in a markedly accelerated polymerization and the highly promoted switchover from the protofibril growth to the lateral aggregation of protofibrils. It was suggested that N-linked carbohydrate chains could interact with αC and BβN regions so as to suppress their releases from the central region of fibrinogen molecule, and play a regulating role of the switchover from the protofibril growth to the lateral aggregation.