The price adjustment process is crucial to almost any macroeconomic issue. Current macroeconomic literature features widely different models ranking from instantaneous price adjustment to completely rigid prices. Professor Andersen provides a comprehensive analysis of reasons why prices may fail to adjust instantaneously to changes in market conditions. This unified treatment will allow the reader to understand the mechanisms at work without becoming lost in technical details. This volume covers both real and nominal price rigidities and integrates existing results from the literature with new results on causes for failures of price adjustment. The analysis of real price rigidities includes inventories, customer markets, search and collusive behaviour. Due to the focus on macroeconomic implications, the analysis of nominal price rigidities is extensive and includes menu costs, informational problems, asynchronized price setting as well as the interaction between price and wage setting. Professor Andersen's own theoretical work on imperfect information, a prime source of price and wage rigidity, is given prominence in the book. The volume is thus a combination of a valuable survey of the literature, and an original expression of future possible research avenues.