Nine patients with active ocular or optic nerve involvement by syphilis who also had concurrent human immunodeficiency virus type-1 (HIV-1) infection are described. The ocular manifestations of syphilis led to the discovery of HIV-1 seropositivity in four of nine cases. Fifteen eyes were affected. Ocular manifestations were: iridocyclitis in three eyes, vitreitis in one eye, retinitis or neuroretinitis in five eyes, papillitis in two eyes, optic perineuritis in two eyes, and retrobulbar optic neuritis in two eyes. Three patients diagnosed with acquired immune deficiency syndrome (AIDS) had the worst initial visual acuities. Six of nine patients had evidence of concomitant central nervous syndrome (CNS) involvement with syphilis. Benzathine penicillin was administered intramuscularly to three patients. All three had relapses. Seven of nine patients treated intravenously with high-dose penicillin had dramatic responses to therapy with improvement in vision and serologies and no evidence of relapse. Regimens accepted for the treatment of neurosyphilis appear to be adequate for the treatment of ocular syphilis in HIV-1-infected patients though further long-term follow-up will be required.