This book examines extensive empirical evidence on the macroeconomic implications of parallel exchange rates in developing countries. Eight case-studies from Africa, Latin America, and Turkey provide detailed evidence on the emergence of parallel exchange rates, their impact on macroeconomic performance, and the criteria for successful exchange-rate unification. A chapter on European dual exchange rates summarizes the contrasting experience of industrial countries. An overview chapter lays out the analytical framework, assesses the evidence, and draws policy conclusions.