The material presented in this book is a result of my work in the field of call center management during the period 1999-2002. The focus is on the perfor- mance analysis and optimization of inbound call centers. Since call arrivals and call-handling times are often random in inbound call centers, this thesis concentrates on the performance analysis and optimization using queueing models. This book describes mathematical methods and algorithms to relate the number of agents and telephone trunks of a given call center configuration to technical as well as economic performance measures. This book has been accepted as a Ph D thesis in Business Administration at the Technical University of Clausthal, Germany. I am indebted to many people for their support during the process of writing this thesis. First of all, I would like to thank my advisor, Prof. Dr. Stefan Helber, for motivating my research to call center related problems. He gently pushed me in fruitful directions and encouraged me to strike a balance between mathematical results and economic implications. Many other helpful suggestions came from him, and his constructive comments on draft versions of this book are invaluable. I am thankful to him and to Prof. Dr. Rolf Schwinn for refereeing this thesis.