The World Health Organization (WHO) is the agency within the United Nations specialized in international public health; its primary objective is to facilitate the attainment of highest possible level of health among all peoples. The UN drug control treaties of 1961 and 1971 mandate the WHO to conduct scientific and medical review of substances proposed to be (re-)scheduled. The main role of the Expert Committee of Drug Dependence (ECDD) of the WHO, in this case, is to evaluate the medical properties of a particular substance in relation with its liability for abuse, while taking into account its medical purposes. Recently, for instance, the WHO recommended the re-scheduling of dronabinol from Schedule II to Schedule III of the 1971 Convention, and advised against the scheduling of ketamine.