Revision with unchanged content. After the Mexican, Asian, and Russian financial crisis, the phenomenon of contagion became increasingly important. Existing studies indicate that various explanations for the transmission of crises exist. This book gives an overview over theories that try to explain contagion caused by portfolio flows of international investors. Theories such as the occurrence of information cascades, the effects of international portfolio diversification and optimization, the importance of information asymmetries, cross-market re-balancing effects, risk aversion, and wealth effects are discussed in detail. The analysis suggests that information asymmetries and changes in risk aversion hold an important role in explaining contagious sellouts. The book addresses itself to economists, policy makers as well as portfolio and fund manager.