The accessory canals make the root canal a very complex anatomico- -morphological part of a tooth. In this study, apices of human single- -root teeth extracted for orthodontic or periodontologic reasons were used. Following fixation with 10% formalin, cleaning with 5% sodium hypochlorite and alcohol dehydration, the samples were evaporated with gold and observed by scanning electron microscop. The results obtained have shown that the accessory canals in the root apical region are by no means exceptions, but occur as a rule. Three to four major orifices of 100—250 ¡.im in diameter and a large number of minor foramina of 10-60 Am could be generally seen. Some of the minor foramina revealed the signs of closure with a cement substance. Accessory canals improve the health tooth perfusion, but in the di-sease affecting the pulp as well as in the endodontic tratment they may present an additional problem, make the treatment more compli-cated and even contribute to its failure.