Optic neuropathy with simultaneous orbital and sinus inflammation is a diagnostic dilemma. Although sinus inflammation was described previously as causative in some cases of optic neuritis, the relatively high rate of asymptomatic sinus opacification in radiologic studies of the general population (as high as 13%) makes this a diagnosis of exclusion. We describe a patient who had optic neuropathy associated with simultaneous orbital and sinus inflammation. Although definitive determination of etiology may not be made without tissue biopsy, cases suspected of having a bacterial etiology may benefit from an initial 48-hour trial of intravenous antibiotics before initiation of systemic corticosteroids.