There is great inconsistency on how "Clinical Guideline Developers" worldwide rate the quality of evidence and strength of recommendations because there are several classification systems in use. Therefore, medical guideline users face profound challenges in understanding articles on Clinical Guidelines. Many researchers are adopting the GRADE system to classify the quality of the available evidence and the strength of recommendations when preparing a manuscript on Clinical Guidelines. The GRADE system has advantages over previous rating systems including being developed by a representative group of guideline developers, patent separation between quality of evidence and strength of recommendations, explicit evaluation of the importance of outcomes of alternative management strategies, and others. Consequently, in this brief review, we describe the reasons underlying the adoption of GRADE.