In July, 1988, more than 300 scientists from 29 different countries gathered at Tiibingen, W. Germany, in order to spend 4 days discussing their favourite trace element, selenium. This meeting continued the good tradition of three previous meetings held in Corvallis/Oregon, 1976, in Lubbock/Texas, 1980, and in Beijing/China, in 1984. Incidentally, the University of Tiibingen provided a unique historical background for a Symposium devoted to recent advances in biochemistry, pharmacology, human nutrition and human health; here, the first independent depart ment of Physiological Chemistry in Germany was founded in 1845. Pro fessor H9Ppe-Seyler elucidated here the hemin structure and his student Friedrich Miescher discovered the nucleic acids. This book contains one-half of the oral or poster presentations which were selected before the meeting was held on the basis of a one page abstract. It is the reader who will have to decide whether this time consuming policy of quality assessment was warranted or not."