A retrospective study of 767 HIV positive patients from a large urban public hospital, 238 of whom were co-infected with syphilis, was performed to determine the prevalence of neurosyphilis. A prevalence of 3% of neurosyphilis in the co-infected cohort was demonstrated. The 7 cases of neurosyphilis ascertained were of the early stage variety, with cranial nerve involvement the predominant focal deficit. Of the 5 cases presenting after initial diagnosis and treatment of syphilis, 4 were felt to be inadequately treated. An overall prevalence of 1% (7/767) was determined for the entire HIV(+) cohort. The majority of the cases of syphilis (90%) were characterized as latent syphilis. Based on these findings, the authors recommend routine CSF examination in all patients who are HIV positive and who present with latent syphilis. Treatment regimens should be maximized in an effort to reduce the prevalence of neurosyphilis in such a co-infected cohort.