This book gives an accessible overview of the role and potential of mathematical optimization in call centers. It deals extensively with all aspects of workforce management, but also with topics such as call routing and the scheduling of multiple channels. It does so without going into the mathematics, but by focusing on understanding its consequences. This way the reader will get familiar with workload forecasting, the Erlang formulas, simulation, and so forth, and learn how to improve call center performance using it. The book is primarily meant for call center professionals involved in planning and business analytics, but also call center managers and researchers will find it useful. There is an accompanying website which contains several online calculators.