Oral fluid is a readily available specimen which can be collected by non invasive procedures and contains many drugs of interest in screening and diagnosis. It is obtained by a painless and non invasive method of sampling; it contains the free fraction of drugs and therefore it could be a good indicator of intoxication state. Oral fluid in fact has the potential for supplying interpretation with respect to blood concentration and impairment with similar detection windows to blood. Drugs of abuse have been investigated in oral fluid for more than twenty years, because of a number of advantages compared to the body fluids traditionally used as substrates for therapeutic drug monitoring, that is blood and plasma, and actually their analysis is becoming more widely used and accepted across a number of testing disciplines. This review summarizes the studies on the determination of different drugs of abuse in oral fluid in the last eight years to elucidate the current status in this area. To obtain useful information about the correct employ of oral fluid in forensic toxicology, the study of some parameters such as collection, storage and stability of drugs, is required. Moreover analytical aspects and interpretation of results must be evaluated. For this purpose the analysis of the latter scientific literature is discussed in detail for the knowledge of the state of the art, with respect to some forensic aspects such as driving impairment or workplace drug testing.