The motor nerves to the eye and the first branch of the trigeminal nerve leave the middle cranial fossa through the superior orbital fissure. Pathological processes around this relatively narrow cleft can give rise to a syndrome which consists of retro-orbital pain, paresis of the ocular muscles, and sensory changes in the distribution of the first trigeminal branch. Pathological processes in the cavernous sinus can produce an exact imitation of this syndrome. Some remarks on the anatomy of this region should precede a comment on the superior orbital fissure syndrome. Anatomy The superior orbital fissure is enclosed by the lesser and the greater wing of the sphenoid bone. Its shape is subject to considerable variation. As a rule it has an elongated pear shape with the broadest part at the nasal side. The long axis, which averages 15 mm. in length, extends upwards, from nasal to lateral, at an angle