At present, there is more and more persistently shown interest in drug-free treatment that can replace or significantly limit the need for drugs and thus affect various aspects of the pathological process, contribute to the regulation of disturbed homeostasis, improve the functional status of the various organs and systems that enhance the body's defenses. One of these methods is the therapeutic use of ozone which receiving considerable spread in our country and abroad. During the last 14 years, we have made a great effort to examine ozone therapy in a scientific fashion both at a basic and clinical level, and we now have some ideas how ozone acts, how and why its toxicity can be controlled and how therapeutic effects can be exerted. There is no need to invoke philosophical speculations because the mechanisms of action are in the realm of classical biochemistry, physiology and pharmacology. This review aims to give the reader the essential information about using ozone in general medicine and dentistry.