<p>Interest in the olive leaf and its chemical constituents has recently been increasing. Its benefits, however, have been known for centuries, and it has been traditionally used to prevent and treat diseases. The main constituent of the olive leaves is oleuropeine one of iridoide monoterpenes, which is thought to be responsible for pharmacological effects. Furthermore, the olive leaves contain triterpenes including oleanolic and maslinic acid, flavonoides (luteolin, apigenine, rutin...), and chalcones (olivin, olivin-diglucoside). Its chemical content makes olive leaf one of the most potent natural antioxidant. Olive leaf is used to enhance the immune system, as an antimicrobial and in heart disease. Folk medicine uses also include hypertonia, arteriosclerosis, rheumatism, gout, diabetes mellitus, and fever. Recently, experimental animal studies have demonstrated hypoglycemic, hypotensive, antiarrhythmic, and vasodilator effects, as well as spasmolytic effect on the intestinal smooth muscle. Antibacterial, antiviral and antiinflammatory activity were also confirmed. The beneficial properties of olive leaf are further enhanced by the bioavailability of its polyphenolic constituents, which are readily absorbed through the gastrointestinal tract, resulting in significant levels in the circulation. Clinical studies to confirm experimental results are needed</p>