This report was derived from cross-sectional and longitudinal analyses of prevalence, pattern, and severity of incisai wear in 64 dental students who had virtually complete dentitions at the first examination and unchanged dentitions at the re-examination. They were first examined in 1991 and re-examined after 24 months in 1993. The average age of the students in 1991 was 23±1.7 years. Assessment of incisai wear was made on stone casts based on silicone impression material in accordance with the Incisai wear Index (IwI). The results showed that the prevalence of incisai wear had not changed during the observation period. The severity of incisai wear for maxillary and mandibular central and lateral incisors had remained essentially the same, whereas the severity of wear of maxillary and mandibular canines had increased during the observation period. There was no statistically significant relationship between age and IwI. The wear pattern found for anterior teeth is discussed in relation to the cuspid protection and the group function theories of occlusion.