During three months (April to June 1997) 1,238 consecutive pregnant women were studied at the time of delivery at the Madariaga public Hospital. Syphilis was confirmed in 26 (2.1%) women, and 15 cases (57.7%) of congenital syphilis were demonstrated in newborns one of whom was a stillborn. Of the syphilitic women 61.5% were 20 years old (average), 65.4% were single, 19.2% had a stable partner and 15.4% were married; 70% of them had finished elementary school (seven years), but despite this discrete level of instruction and that they were benefited with free health attention, 73% of them had not started or completed the pregnancy control. None of these women acted as sexual workers or were drug users; 57.7% were unemployed and the remainder worked as domestic servants or were still going to school. Menarca started at 13 (average) and the age of the first sexual activity was 15 (average). The distribution of the cases of syphilis within the city area shows four clusters that coincide with the lower income population, but not with marginal groups. The failure to submit to medical control during pregnancy among syphilitic women is directly linked with an increased risk for congenital syphilis. The specific prevalence of syphilis in women (20 years old or less) pregnant or not, shows an alarming hidden epidemic situation. An interinstitutional and communitary program, with direct interventions within the detected population clusters, is now underway in order to control syphilis. Undesired pregnancy and syphilis seem to be associated with adolescent unsafe sex conducts. A coordinated program between Public Health Service and National Misiones University is operating, visiting home by home, in order to decrease or eliminate congenital syphilis and is considered a priority health problem. Unfortunately, if sexual conducts do not undergo changes in the near future, at least by the correct use of condoms, HIV will replace syphilis.