The oral cavity, a very complex and unique milieu due to its dual function, respiratory and digestive, is the only place in the body where the mineralized tissue is exposed to the external environment. In this environment there are complex interactions between various surfaces: host soft and hard tissues, food, air and microorganisms. Saliva is in the middle of this environment and tries to cope with an ever-changing milieu. It includes a large number of inorganic and organic compounds, which act as a "mirror of the body's health". In addition to its other functions, saliva could constitute the first line of defence against oxidative stress. The body contains a number of protective antioxidant mechanisms. Saliva is also rich in antioxidants. We review the current available data and from our laboratory concerning antioxidant capacity of saliva. Substantial data are available in literature on the role of reactive oxygen species and antioxidants in diseases, but few information is available on oral pathology. Due to its composition and functions, saliva could have a significant role in controlling and/or modulating oxidative damages in the oral cavity.