The possible existence of acquired dysfibrinogenemia was investigated in blood samples from 30 patients with liver cirrhosis, 15 newborns and 30 healthy control subjects. Alterations of thrombin time were found in newborns and in 14 cirrhotic patients; glucide fraction levels were measured in these subjects and an increase in sialic acid content was observed. Its functional role was studied by comparing thrombin time and electrophoretic mobility of purified and desialylated forms of fibrinogen. We observed a thrombin time normalization, which was initially prolonged upon the removal of the sialic acid. The anodic electrophoretic mobility underwent changes due to the removal of sialic acid.