BACKGROUND Even today screening for congenital syphilis must be performed and confirmed by appropriate serological tests and bacteriological samples. METHODS A newborn presented with an apparently materno-fetal or viral fetal disease. It was in fact congenital syphilis. The mother exhibited no risk factors for syphilis. Systematic serological search for syphilis was negative in the mother at 11 weeks of amenorrhea. No signs of primary or secondary syphilis had been observed during pregnancy. At twenty-nine weeks of amenorrhea, the mother presented a menace of preterm delivery and no tocolysis at 31 weeks. Examination of the newborn revealed clinical signs of aterno-fetal infection, without specificorientation. Initial bacteriological and virological analyses were negative. Screening for specific Treponema pallidum M-type immunoglobulines (IgM) on the 9th day of life, confirmed the diagnosis of congenital syphilis. CONCLUSIONS Diagnosis of congenital syphilis must not be eliminated during early serological screening: clinical suspicion must lead to further anamnesis again and serological tests both in the newborn and the mother.