A sound understanding of the ethmoid sinus complex forms the basis of comprehensive sinus surgery. It is important to understand the anatomical boundaries of the ethmoid cavity and the “correct shape” of a dissected cavity. Complete uncinate and ethmoid sinus dissection allows for easier access for frontal and sphenoid surgery as well as the skull base. This chapter will provide a comprehensive step-by-step approach to performing comprehensive ethmoid sinus surgery.