In September, 1987, the authors saw a 25-year-old female patient with retinal perivasculitis, cystoid macular edema and papilledema in her right eye. The left eye was normal. Visual acuity was 0.2 (OD), 1.2 (OS). After conventional infections had been ruled out systemic methylprednisolone therapy was instituted, but the patient's condition deteriorated. In May 1988 she presented with papilledema and a "neuroretinitis"-like finding in her left eye; in her right eye advanced optic nerve atrophy; visual acuity was 0.1 (OD) and 0.07 (OS). The laboratory workup revealed an acute phase of a chronic Borrelia burgdorferi infection, with total immunoglobulins (immunofluorescence test) of 1:1280 and an IgM of 1:650 (normal ranges: total Ig up to 1.80, IgM up to 1:40). MRI showed multiple paraventricular and subcortical demyelinating lesions. However, the cranial CT scan was normal. After 14 days' treatment with doxycycline 200 mg/d, visual fields and acuity improved to sc 0.2 (OD) and sc 0.1 (OS) (July, 1988). This case of intracranial demyelinizating lesions associated with bilateral optic neuritis in a serologically determined Borrelia burgdorferi infection is the first of its kind described in the literature.