In September 1998 experts from 19 countries came together for an interdisciplinary discussion of the function of animal peroxidases, a family of enzymes embracing myeloperoxidase, eosinophil peroxidase, thyroid peroxidase and lactoperoxidase. Their papers have been updated for publication, yielding a wide-ranging overview of the state of the art. The chapters cover a wide range of topics, including three-dimensional structure of representative family members, their biosynthesis and intracellular transport, mechanism of action as well as applications to clinical medicine. They are of clinical relevance in, for example, arteriosclerosis, multiple sclerosis, infections, tumorigenesis, rheumatic diseases and hypothyroidism. This book forms an excellent introduction for anyone interested in the peroxidase family of enzymes.