In this study, scanning electron microscopy (SEM) was used to describe in detail the surface structure of geographic tongue. Tissue samples from the anterior part of the tongue were removed from 15 patients with geographic tongue and from 15 control subjects. Normally, the surface mucosa of the tongue was covered by filiform papillae, which consisted of the body and hairs. The mucosal surface of the body was smooth with some desquamating cells, but hairs were covered by an extensive plaque of microorganism. With SEM, the surface of geographic tongue contained 3 different types of mucosa: atrophic area, white margin, and area of normal appearance. On the atrophic area, the mucosa formed low elevations, and hairs were lacking. At high magnification, the superficial cells of the low elevations were polygonal, and they had parallel or branching microplicae. The white margin contained many desquamating cells, which had broken microplicae or no surface structures. Here the inflammatory infiltrate of the epithelium and that of the subepithelial connective tissue was moderate. On the normal-appearing area, desquamation of the mucosa on the papillar bodies was more pronounced than normally. On every specimen was a fissure, on the walls of which the superficial cells had broken microplicae and knob-like structures. The adherence of candidal hyphae within the superficial cells was seen in the area of the fissure. On the geographic tongue some fungiform papillae with taste pores were seen.