In recent years, due to the need to elaborate the amount of information available from the scientific literature, the meta-analyses and systematic reviews have become very numerous. The meta-analyses are carried out to evaluate the association between two events when single researches haven't provided comprehensive data. On the other hand, a good meta-analysis must satisfy certain criteria, from the selection of the studies until the evaluation of the outcomes; to this purpose, the application of methods for quality assessment is a crucial point to obtain data of adequate reliability. The aim of this review is to give some introductory tools for a critical approach to meta-analyses and systematic reviews, which have become useful instruments also in occupational medicine.