In a retrospective study encompassing 42 months (January 1984 through July 1987), 12 patients were identified as having both neurosyphilis and acquired immunodeficiency syndrome. These patients constituted 44% of the entire group meeting rigorous diagnostic criteria for neurosyphilis and 1.5% of all patients hospitalized with acquired immunodeficiency syndrome. The typical patient with acquired immunodeficiency syndrome and neurosyphilis was young (mean age, 37 years) and male (83%). All had serological evidence of syphilis in both blood and cerebrospinal fluid. Syphilitic eye disease was surprisingly common in this group, occurring in 5 (42%). Four patients (33%) had been previously treated for syphilis. In 2, treatment for latent syphilis had been completed 3 and 5 months, respectively, before neurosyphilis was documented. Neurosyphilis is not uncommon in patients with acquired immunodeficiency syndrome in our population. In light of its diverse manifestations, syphilis should be considered in the differential diagnosis of any human immunodeficiency virus type 1-infected individual presenting with neurological, psychiatric, or ophthalmological disease.