The Ministry of Health of Chile, aiming to improve the quality of clinical practice guidelines, gradually incorporated the GRADE system (Grading of Recommendations, Assessment, Development and Evaluation) to develop evidence based recommendations. This system summarizes and evaluates the certainty of the available evidence. It moves from evidence to decision in a systematic and transparent manner, based on four main dimensions: balance between benefits and harms, certainty of evidence, patient's values and preferences and use of resources. The GRADE system produces strong and conditional recommendations. Strong recommendations provide confidence that the favorable consequences of an intervention clearly outweigh the adverse consequences, or vice versa. These recommendations apply to a broad range of patients and circumstances. Conditional recommendations, however, indicate that there is a close balance between favorable and unfavorable consequences of the intervention, there is uncertainty in the magnitude of benefits or adverse effects, there is uncertainty or variability in values and preferences of individuals or costs are not justified. These recommendations apply to many patients, but not all of them: ideally they should be discussed with each person. To achieve a better implementation of the recommendations made with GRADE methodology, health professionals should know the meaning of strong and conditional recommendations and they should be able to critically assess of them.