Book excerpt: Research on the reliability and validity of assessment centers (ACs) has been ongoing for at least 50 years and continues to this day. The assessment center method is a technique or process that is used to assess individual performance and potential. One of the most heavily researched topics over the last 30 years has been the internal structure of AC ratings that assessors make on rating dimensions after the completion of each exercise. This volume, with contributions from experts from around the world, looks at Dimension-Based Assessment Centers, Task-Based Assessment Centers, and Mixed-Model Assessment Centers. All three perspectives are presented in different sections, and a summary of these diverse perspectives is given at the end of the book.