The case of a 40-year-old patient who underwent an unsuccessful cadaver kidney transplantation and was treated with ethambutol and isoniazid is reported. A bilateral retrobulbar neuropathy with an unusual central bitemporal hemianopic scotoma was found. Ethambutol was stopped and only small improvement of the visual acuity followed. Isoniazid was discontinued later, followed by a dramatic improvement in the visual acuity. The hazards of optic nerve toxicity due to ethambutol are known. We emphasize the potential danger in the use of ethambutol and isoniazid.