A representative sample, 55%, of the patients treated endodontically by undergraduate students in a teaching clinic during the years 1963 to 1969 were reexamined 10-17 years later. Gutta-percha/Kloroperka-NO root fillings (282), classified as having surplus material at the time of treatment, were evaluated in follow-up radiographs. In about 80% of the cases of overfilling, no excess root filling material could be traced at the reexamination. In a few cases only, the appearance of the excess material was nearly identical to that at the time of treatment, whereas the remaining overfillings (18%) showed a reduced size. Among the recorded variables only one seemed to have a major impact on the prognosis--namely, the presence or absence of an apical radiolucency at the time of treatment, indicating that infection was the important factor when failures occurred. Apical overfilling per se had little influence on the long-term healing result as judged radiographically.