Meta-analysis was introduced as an effective means to integrate research findings. With regard to its definition and interpretation, however, it has remained rather controversial. If meta-analysis is defined as a series of review methods including statistical analysis and/or synthesis of the summary statistics of the studies considered, a statistical nucleus becomes evident. The relationship between summary statistics (e.g. significance levels and effect sizes) and their psychological interpretation, on the other hand, is unclear. It is therefore argued that in many instances it is impossible to link a psychological interpretation to the results of meta-analytic operations.