We studied 21 cases of adult conjunctivitis caused by Neisseria gonorrhoeae, confirmed by either Gram's stain or culture, that were seen between 1972 and 1986. The patients, typically young men, had irritation or pain, a copious purulent discharge, and marked conjunctival inflammation. Keratitis, anterior chamber inflammation, periocular edema and tenderness, gaze restriction, and preauricular lymphadenopathy were common. All patients were hospitalized and treated with high doses of parenterally administered antibiotics. Two patients had severe ulcerative keratitis at initial examination, which ultimately resulted in light-perception visual acuity, despite antibiotic therapy and keratoplasty. In the remainder of the patients, corneal involvement was milder and transient, and treatment with parenteral penicillin and topical antibiotics was uniformly effective in reversing the course of the infection and preventing significant visual loss. Careful ophthalmologic and microbiologic monitoring is suggested to prevent possible complications caused by penicillin-resistant strains.