In a study of the cavernous sinus in 70 specimens, the lateral wall of the sinus was found to be formed by two layers: a superficial, dural layer and a deep layer. The latter was formed by the sheaths of nerves III, IV, and V 1,2 plus a reticular membrane extending between the sheaths. This membrane was often incomplete, particularly between the sheaths of nerves III and IV above, and V1 below. These findings do not conform with the descriptions of a single dural layer of the lateral wall, with nerves III, IV, and V 1,2 embedded in it, nor to other descriptions showing the cavity of the sinus divided into two compartments by a septum close to the lateral wall, with nerves III, IV, and V1 located within the septum. In the present study, the superficial and the deep layers of the lateral wall were found to be loosely attached to each other and easy to separate. In no case was a superficial compartment of the sinus found to be present between the two layers, and the nerves were never found to be running embedded in the superficial layer.