This clinical article presents and describes the endodontic treatment of a mandibular second premolar exhibiting a total of four separate root canals. This incidence in mandibular second premolars is particularly rare in the international endodontic literature. Only some infrequent cases of mandibular second premolars with four canals have been presented; however, this was done without the use of the operating microscope. The use of magnification is a prerequisite to locate and to confirm the exact number and position of canal orifices and to complete successfully the endodontic treatment. The endodontic treatment of the mandibular second premolar presented in this article was conducted with the aid of the operating microscope and photos of the pulp chamber floor that were taken under different steps of magnification (8x, 12.8x, and 19.1x).