This paper is an update of the current knowledges about saliva components whose assays are of biological interest and have been validated. It begins by a recall of saliva physiology: role, flow rate, main components and their mode of entry into saliva. Infectious agents and their markers are not reviewed. Peptidic molecules (catecholamines, short hormonal peptides), lipids, minerals (Na, K, Li), proteins (hormones and immunoglobulins) and steroids are examined. Assays of hormonal steroids (cortisol and sexual hormones) are described in more detail because these assays have been largely used since 1980 (many papers appeared using these methods) and are well validated. This method which allows an unstressful sampling versus venipuncture is of great interest, particularly for cortisol. Saliva assays present a lot of advantages when compared to blood assays: the sampling is very easy to do especially in a non medical environment, it does not disturb intimacy when control is needed and the risk of contamination for the laboratory technician is lower than for blood. Moreover, for molecules which are linked to blood protein carriers, the saliva concentration reflects the free blood concentration.