Obstetric patients with serologic evidence of syphilis should have cerebrospinal fluid (CSF) analysis to determine the presence of tertiary disease. In the present study, 19% of untreated and asymptomatic patients with serologic evidence of syphilis were found to have tertiary syphilis following examination of CSF. Despite maternal therapy, 11% of the infants born to mothers with syphilis had reactive serum and CSF involvement as documented by the presence of a fluorescent treponemal antibody absorption (FTA-ABS)-specific IgM.