Early diagnosis of congenital abnormalities of coagulation may be masked by the clotting defects associated with the newborn period and mistaken for hemorrhagic disease of the newborn. A case is presented which illustrates this problem. To exclude a congenital defect, a careful family history should be obtained and a complete coagulation study performed on all infants with severe hemorrhagic manifestations. The diagnosis of hemorrhagic disease of the newborn should not be assumed in such cases. If there is evidence to support the diagnosis of a congenital abnormality, either from the family history or from the coagulation studies, or should there be a lack of response to vitamin K in an infant with severe bleeding, replacement therapy with plasma or serum should be instituted immediately. Repeated coagulation studies will eventually demonstrate the congenital abnormality and should be performed in suspected cases.