Few data have been collected regarding the prevalence and quality of root canal therapy in American populations. European studies of various populations were used as a model for the evaluation of the prevalence and technical standard of endodontic treatment in a patient group seen for screening at a United States dental school. Full-mouth radiographic series were examined for the presence of root fillings, periapical pathologic conditions, and coronal restorative status. The obturation density and length were also recorded. Of 5272 teeth examined, 5.5% had root fillings. Periapical disease was evident in 4.1% of all teeth and 31.3% of root-filled teeth. Lesser-quality root fillings were more strongly associated with periapical disease than were higher-quality obturations. In addition, only 42% of the obturations could be considered technically satisfactory. Such data suggests that more research must be directed toward the study of factors that affect treatment outcome.