Background and design.- Meta-analysis as a def¬inition is the integration of the results of several dif¬ferent studies performed for a particular subject and statistical analysis of research findings. This method is a systematic, statistical evaluation of multiple investi¬gations with their analytic and common findings. Results.- In this study we used meta-analysis method in order to verify the effect of GEA (a tumor marker) in differential diagnoses of malignant and benign pleural fluids. As a result of synthesising dif¬ferent studies on this subject we used Weighted aver¬ages, Quantative integration, Stouffer, Woolf, Mantel-Haenszel methods. Conclusion.- In nine different researches CEA lev¬els has been found elevated in the malign group. When meta-analysis has been applied this theory has been enforced. Therefore meta-analysis also showed that GEA levels are higher in the malign group in con¬trast to the benign group.