Prior to the introduction of functional endoscopic sinus surgery, several surgeons had begun to use telescopes to perform surgical procedures in the nose and sinuses. However, the central concepts of functional endoscopic sinus surgery evolved primarily from Messerklinger's endoscopic study of mucociliary clearance and endoscopic detailing of intranasal pathology. The popularity of a combination of endoscopic ethmoidectomy plus opening of secondarily involved sinuses grew rapidly during the latter part of the twentieth century, and endoscopic intranasal techniques began to expand to deal with pathology other than inflammation. We present a review of the evolution of knowledge regarding the pathogenesis of inflammatory sinus disease since that point in time, and of the impact that this has had on the management of inflammatory sinus disease. We also detail the technological advances that have allowed endoscopic intranasal techniques to expand and successfully treat other pathology, including skull base and orbital disease. In addition, we describe evolving technologies which may further influence development within this field.