A 68-year-old woman with ovarian cancer suffered a loss of visual acuity and color perception after inadvertent overdosage with the antineoplastic agent cisplatin. Her acuity returned to normal but a tritan color defect persisted more than a year later. Her electroretinogram was stable between 7 weeks and 15 months after cisplatin administration, with a negative-type scotopic response, but also reduced cone b waves and a loss of some scotopic oscillatory potentials. With light stimuli between 10 and 100 ms in duration, the photopic on-responses were markedly reduced while the off-responses were normal or close to it. This case suggests that cisplatin may selectively injure on-pathways in the retina and indicates the need to expand the list of disorders that may cause a negative-type electroretinogram.