Among 829 participants of the Veterans Administration Dental Longitudinal Study examined over four triennial cycles, 97 persons (11.7%) had one or more unerupted third molars, for a total of 151 teeth, when the study was initiated. During the first 10 years of the study, 10 subjects had 14 unerupted third molars extracted, while in 10 persons 11 third molars erupted. Four of the latter persons each had one third molar removed subsequent to eruption. Three of the 11 erupted third molars were in functional occlusion. The position of 4 of the 11 "erupting" third molars appeared to remain unchanged relative to radiographic landmarks. Thus, their apparent clinical eruption may have been due to a reduction in the level of the gingival tissue in the area distal to the second molar tooth in association with periodontitis. The eruption of third molars in older adults appears to be a more frequent phenomenon than was previously recognized. Most erupting third molars had some associated pathologic condition, including caries and periodontitis.