Introduction. Neurosyphilis is an uncommon manifestation of central nervous system (CNS) infection caused by Treponema pallidum. Cases. We report three cases of neurosyphilis. Case 1 presented with ocular involvement: right optic atrophy and left optic neuritis; case 2 had a meningovascular form, with ischemic stroke; and case 3, a meningeal form, presented with headaches as the main complaint. Discussion. The cases reported had distinguished forms of neurosyphilis. Serologic diagnosis depends on the presence of antibodies: Veneral Disease Research Laboratory (VDRL) -not specific -and/ or Fluorescent Treponemal Antibody Absorption (FTA-ABS) -specific. Conclusion. In the cases above cerebrospinal fluid FTA-ABS was a diagnostic clue for neurosyphilis even though unreactive serum VDRL was found.