PREAMBLE Many clinically important drugs, such as aspirin, digitoxin, progesterone, cortison and morphine, have been derived directly or indirectly from higher plants. Less well-recognised but of great clinical importance are the widely used drugs from fungi such as the antibiotics, penicillin and griseofulvin, the ergot alkaloids and cyclosporin. During the last two decades there has been an increasing recognition of the role of the human immune system for maintaining good health. Diseases now associated with immune dysfunction such as cancer, chronic fatigue syndrome, AIDS/HIV, hepatitis and autoimmune conditions are increasingly coming to the forefront and being given special attention from medical researchers and clinicians alike. Historically, the larger fungi, the mushrooms, have had a long and successful medicinal use especially in traditional Chinese clinical medicine for many forms of immune disorders. Chinese Pharmacopeias document the use of well over 100 species of mushroom by practitioners of traditional Chinese medicine, for a wide range of ailments. Many of these mushroom-derived medicinal products are now produced by major Japanese, Korean and Chinese pharmaceutical companies. Many of these products are being used worldwide by holistically oriented physicians, chiropractors, herbalists and naturopathic physicians in a clinical environment. To date, Western, medicine has made little use of these products in part due to their complex structure and lack of acceptable pharmaceutical purity. Mushrooms are not a taxonomic group but do include well over 12,000 species which have macroscopic fruit-bodies, the mushrooms, which are large enough to be seen by the naked eye. Mushrooms are increasingly being evaluated in the West for their nutritional value and acceptability as well as their