Objective : The aim of this study was to investigate risk factor, precaution and treatment of aspirated foreign body during dental procedure. Material and Methods : Twenty cases of accidental aspiration of the foreign body, which removed by bronchoscopy at the Asan Medical Center between 2008 and 2012, were analyzed retrospectively. Results : Ten cases of accidental aspiration were occurred during dental procedure. Symtoms include cough(65%), dyspnea(50%), sputum(25%) and wheezing(25%). The most common location of foreign body was right bronchial tree(50%), left bronchial tree(45%) and carina(5%). Patients risk factors were chronic obstructive pulmonary disease, lung cancer, pulmonary tuberculosis, esophageal cancer and vegetative state. Conclusion : Accidental aspiration or swallowing of dental instrument or material is not uncommon accidents in dental practice. Most foreign bodies enter into gastrointestinal tract spontaneously. But aspiration into broncho-trachea can be more serious events and must be treated as an emergency situation. Prompt emergency treatment and removal of the foreign body is necessary to avoid complication. Dentists must have knowledge about the precaution and be ready to deal with foreign body aspiration during dental procedures.