The congenital syphilis is an infectious fetopathy which is able to affect the whole organism. In most cases symptoms are not obvious before week fourth to twelve of life. The infection of the mother is the precondition for the child's disease. The placental transfer takes place after the fifth to sixth month of gestation. We report about an eight week old baby with congenital syphilis. The positive maternal laboratory findings in the 4th month of pregnancy have been interpreted as a completely cured earlier infection causing a sero scar. The diagnosis became evident by serological tests detecting reactivation of maternal infection in late pregnancy and the clinical signs of acute infection of the child. CONCLUSIONS There is a high risk of reactivation of maternal syphilis in the third trimenon even if the mother does not show any symptoms. In this case further serological tests in the prenatal care and careful examination of the newborn must be initiated.