The most comfortable positioning for a dental operating microscope (DOM) during nonsurgical endodontics for operators was investigated. Operators were categorized into 3 groups according to height. We recorded the time taken to obtain magnified images, and the angles of binoculars, microscope body, and the mirror to floor surfaces. For the group of shorter operators, observations were also made with an angled optics or a short objective lens (200 mm). It took longer to observe the mandibular molars than maxillary in every group. Although the differences in angles among each group were not remarkable for maxillary observation, we confirmed significant differences for the mandibular. Shorter operators had to adopt a strained position for mandibular observation in a standard setup but were more comfortable using angled optics or a short objective lens. By understanding the proper position, operators could learn to perform microendodontics more efficiently.