Over the past decade, herbal medicine has become a topic of increasing global importance, with both medical and economic implications. In developing countries, as much as 80% of the indigenous populations depends on traditional systems of medicine and medicinal plants as their primary source of healthcare. Within the European Community, herbal medicines represent an important share of the pharmaceutical market, with annual sales in the range of US$7 billion. In the United States, the sale of herbal products has skyrocketed from $200 million in 1988 to >$3.3 billion in 1997. Such widespread use of botanicals throughout the world has raised serious questions concerning the quality, safety and efficacy of these products. Thus, accurate scientific assessment of herbal medicine is a prerequisite for global harmonization of herbal health claims. In 1995, as part of its overall global strategy of "Health for All" and due to numerous requests from the member states, the Traditional Medicine Program of the WHO began the extensive task of reviewing the world's scientific literature of commonly used herbal medicines and publishing this information in monographs. The WHO monographs are technical reviews of the quality, safety and efficacy of commonly used herbal medicines and are intended primarily to harmonize the proper use of herbal medicines throughout the world.