Ozone has been successfully used as a therapeutical agent for the treatment of various diseases. In spite of achieving many positive results its clinical use remains controversial. In dentistry it is used for the treatment of gingival and periodontal diseases, peri–implantitis, infection control, hypersensitivity, temporomandibular disorders, radiotherapy induced mucositis, lichen planus etc. The aim of this short review is to discard skepticism regarding ozone therapy and to explain its biological actions and uses.