Lingual mandibular cortical defects (Stafne's defects) are relatively uncommon in recent as well as past populations, but while this condition is often discussed in clinical reports, they are rarely the subject of anthropological research. In this paper, the prevalence of Stafne's bone defects in skeletal samples from Late Neolithic, Late Roman, Medieval and Modern Portugal is investigated (N = 704 complete mandibles and 111 incomplete mandibles). The aims of this paper are threefold: (1) to present and analyse for the first time in Portuguese osteological record prevalence data on Stafne's bone defect, (2) to analyse variations in defect prevalence between skeletal samples from a wide temporal array and (3) to verify if more tenuous lesions in which resorption of the lingual cortex was not yet extensive had the classic radiographic appearance described by Stafne in order to validate the hypothesis that lesions are present clinically in many more cases than published figures indicate. In all cases, differential diagnosis against other conditions that mimic Stafne's defects, namely odontogenic lesions, cysts and neoplasms, was done. In all samples, the evidence of Stafne's defect occurred in 12 individuals (1.7%), and males (2.84%) were more frequently affected than females (0.61%). When incomplete mandibles were considered, only one left fragment (0.90%) exhibited Stafne's defect. Accurate identification of all examples of Stafne's bone defects in antiquity is thought to represent an important contribution to elucidate which factors may be responsible for this trait's cultural, ecological, temporal and geographical patterning. Copyright © 2010 John Wiley & Sons, Ltd.