Based on the classic adverse selection model, this book sets up the cyber "lemons" market model and analyzes the basic rule of asymmetric information. This book focuses on the topics as following: Is there "lemons" in e-commerce market? What rule do the cyber "lemons" characterize? How to build the cyber "lemon" market model? What is the particularity of adverse selection in cyber markets? What is more, how to eliminate or avoid the cyber "lemons"...