The behaviour of market prices is a fascinating subject for researchers. Opinions vary substantially. from the view that prices accurately and quickly reflect relevant information to the other extreme that prices are not rationally determined and are hence to some degree predictable. This diversity of belief about the efficiency of markets is reflected in these proceedings of the NATO Advanced Research Workshop on "A reappraisal of the efficiency of financial markets." The thirty-one workshop papers cover stock. currency and commodity markets. We are pleased to have contributions on markets...