Paranasal infections and inflammatory processes involving the orbits have been described, as have primary orbital conditions that may mimic acute sinus disease. Most common are bacterial and fungal sinus infections with secondary orbital spread, diseases for which the otolaryngologist-head and neck surgeon must be skilled in diagnosis and management in order to minimize sequelae. Optic neuritis arising from such infections requires prompt recognition and aggressive treatment if vision is to be preserved. The most common causes of unilateral proptosis, Graves' orbitopathy, and pseudotumor may in their early stages mimic orbital spread of paranasal infections. Recognition of these entities and ophthalmologic consultation are critical to their appropriate management.