The internal anatomy of the root canal system determines the parameters under which the endodontic treatment will be carried out. Factors such as knowledge of the possible anatomical variations, correct radiographic interpretation, and tactile examination of the walls, are crucial for the correct detection of multiple canals. Morphological variations of many teeth have been reported in the literature. The objective of this article is to describe the approach followed for the endodontic treatment of a mandibular first premolar with two root canals. A female patient with 67-year-old came to the dentistry course for treatment of chronic periapical abscess. The result was satisfactory with shows the control radiograph after twenty-three months.