Meta-analysis is a leading methodology used in systematic secondary researches. Review Manager software is the main tool used by leading world expert groups for meta-analysis. The authors analyzed the features of meta-analyzes evaluating the results of surgeries. It is shown that the majority of baseline clinical parameters correspond to normal distribution (in accordance with central limit theorem) considering the fact that surgical outcomes depend on various and often unpredictable factors. Moreover, multiple heterogeneous variables are compared in the meta-analysis due to the differences in diagnostic scales and methods of evaluating the results in primary researches. Therefore, both absolute and standardized measurements are required for these purposes. The authors describe the features of meta-analysis for dichotomous, continuous and skewed data, as well as for ordinal outcomes, time-to-event, counts and ratios. These data are useful to interpret numerical values, objectively evaluate the majority of surgical outcomes and predict the effectiveness of interventions.