Our aim was to evaluate the incidence of histological abnormalities in soft tissues surrounding impacted third molar teeth when there were no pathological conditions apparent on the corresponding radiographs. Ninety-six dental follicles were collected from third molar teeth of 63 patients. No tooth had a follicular space greater than 2.4 mm as measured on the panoramic radiograph. Specimens were examined by each of three oral pathologists, and only those independently diagnosed as cystic by all three pathologists were considered diseased. A diagnosis of dentigerous cyst was made in 31 cases; 22 of 60 mandibular specimens (37%) and nine of 36 maxillary specimens (25%) were affected. No disease other than dentigerous cyst was seen. We conclude that the incidence of dentigerous cyst associated with impacted third molar teeth is higher than reported in radiographic studies alone. The importance of histological diagnosis of dentigerous cyst should be evaluated further in the light of this unexpectedly high incidence of microscopic disease.