This was a study of the effect of functional endoscopic sinus surgery (FESS) on the ciliary regeneration of maxillary sinus mucosa in patients with chronic maxillary sinusitis, using objective quantitative methods. Twenty specimens from the mucosa of both the superolateral wall and the ostium of the maxillary sinus were sampled during FESS and then six to 12 months later. They were light examined first by light microscopy and then by scanning electron microscopy in combination with image analysis software in order to study the cilia under higher magnification and to calculate proportion of the field that was ciliated. Samples were taken and studied at Cairo University hospital. This study showed that the maxillary sinus mucosa in chronic sinusitis is capable of regeneration and could return towards normal with the improvement of ventilation and drainage of the maxillary sinus following FESS. There were no significant changes in the degree of glandular hyperplasia, goblet cells or pathological glands after surgery.