This volume offers a collection of articles written by speakers at the 68th Annual Symposium of the Biochemical Society held at the University of Leeds in April 2000. The articles present an up-to-date view of protein folding in vitro and in vivo , the role of chaperones in folding, and the consequences of protein misfolding, for example in amyloid diseases. In addition, simulations of folding mechanisms, protein design principles, and protein engineering to produce novel enzymes are discussed. The chapters highlight successes in these areas, and point the way forward in these disciplines. The articles describe the biology of a yeast prion, using techniques spanning structural biology to yeast genetics to reveal how this protein can cause the inheritance of new traits and explains some of the amazing feats by which protein folding is chaperoned in cells. They also provide guidelines for the assembly of novel coiled-coil structures and highlights how environmental screening has been used to produce new enzymes capable of reducing nitrate esters and theire use in the degradation of explosives. In addition, the approaches of DNA shuffling and phage display and their use in the creation of evolved protease inhibitors and tackles the immensely complex biological and biophysical problem of how a membrane protein folds are examined.