The purpose of this study was to describe clinical, stereomicroscopic and light microscopic findings for fissured tongue in 17 patients and compare them with 17 normal controls. Clinical symptoms were found in 13 of 17 patients who complained of scoreness of the tongue. Usually the symptoms lasted more than 3 years. In 15 cases, fissures involved the entire tongue, while in 2 cases, only the edges of the tongue were affected. In all patients, papillae of varying sizes were found in the area of fissures. The papillae were easily noted using stereomicroscopy on fixed-tissue specimens, but could also be seen with the naked eye during careful clinical examinations. Light microscopic studies indicated that the number of inflammatory cells was far greater in the mucosa of fissured tongues than in normal tongues, and this inflammation was not confined only to the fissures. The rete pegs of the epithelium were longer in fissured tongues than in normal tongues, 800 (+/- 79) micron and 620 (+/- 69) micron, respectively, (p less than 0.001). The lamina propria was also thicker in fissured tongues than in normal tongues, 390 (+/- 74) micron and 170 (+/- 61) micron, respectively, (p less than 0.001). In normal tongues, keratohyaline granules were observed in the filiform papillae around the area of hairs but these granules were absent in fissured tongues.