Resumen: The volume of health-care literature is growing at an increasing rate, with a huge amount of studies difficult to process. Therefore, we need tools or techniques to synthesize the information to help us in clinical decision-making. In fact, the available body of evidence ranges from single studies to umbrella reviews. In this scenario, evidence-based clinical decision-making requires knowing what type of evidence to use in every situation. However, a prerequisite for optimal decision-making is a greater understanding by professionals of the different techniques used to analyse their strengths, limitations and utilities. The purpose of this chapter is to take a journey from qualitative reviews to umbrella reviews. We start the tour on a fundamental point: term definitions, showing the variability among different authors. We go on to describe the differences, advantages, disadvantages and uses of different types of evidence, from individual studies to the `more specific methods¿ for knowledge synthesis, both qualitative and quantitative syntheses (systematic reviews, meta-analysis, network meta-analysis). Finally, in the last part of our journey, we compare the strengths and weaknesses of different evidence synthesis methods from the more traditional or specific to the more general or broader reviews (umbrella reviews, overviews of reviews, meta-epidemiologic reviews). Systematic reviews are at the top of the evidence pyramid. However, the number of systematic reviews published is increasing at a high rate, and decision-makers need to evaluate more evidence to answer their questions. Systematic reviews of existing systematic reviews, known as umbrella reviews, provide an overall examination of the body of information that is available for a given topic. Despite the limitations and weaknesses of tools to appraise and synthesize evidence, systematic reviews and umbrella reviews, including overviews of reviews and meta-epidemiological studies, continue to be the best tool for an approximation to the truth, in evidence-based terms.