In many scientific fields, meta-analysis has become the standard method for summarizing research findings. The number of published applications of the method has been steadily growing in the last 25 years and the statistical procedures of meta-analysis continue to become more and more advanced. This book provides a comprehensive treatment of the statistical procedures for meta-analysis with correlations as an effect size. In the first part, the statistical fundamentals of existing meta-analytical approaches are explained in detail. Fixed as well as random effects models are described and several refinements to improve the performance of the procedures are presented. Additionally, the different procedures are compared from a theoretical viewpoint. In the second part, the results of a comprehensive Monte-Carlo study are presented to evaluate the performance of the major approaches in a large set of possible situations. It shows when the procedures of commonly applied approaches work and when they fail to provide reliable results. The book is relevant for researchers in organizational and educational psychology, for example, as well as other areas where correlations represent an effect size of vital interest.