Herbal drugs have been used for centuries to cure diseases and relieve symptoms. The findings on efficacy until late into the 19th century were based on experiences and observations of healers. They were usually passed on by word of mouth or are preserved in old books. Since at that time they did not have any ideas on the mechanism, they documented a purely empirical experience and did not critically examine the possibilities and limitations of the healing power of a plant or drug. Thus one finds in old herbal books on medicinal plants and drugs, long lists of diseases or ailments that a drug can cure or at least influence ("Indications Poetry"). In modern times, and increasingly in the 20th century, we have critically screened and scientifically scrutinised the areas of use listed in the old works. This process is reflected among others in the drug monographs of the Commission E and later in those of the ESCOP and the WHO, and now also in the monographs of the HMPC. In these monographs only plausible indications for a drug are listed under the heading "Areas of use", i.e. if their effectiveness on a particular disease or a particular symptom can be considered either confirmed experimentally or theoretically well founded. These areas of use are listed in the Medicinal Plant Encyclopaedia under the heading "Recognised medical uses".