One approach to clinical decision-making requires the integration of the best available research evidence with individual clinical expertise and patient values, and is known as evidence-based medicine (EBM). In clinical decision-making with the current best evidence, systematic reviews have an important role. This review article covers the basic principles of systematic reviews and meta-analyses, and their role in the process of evidence-based decision-making. The problems associated with traditional narrative reviews are discussed, as well as the way systematic reviews limit bias associated with the assembly, critical appraisal and synthesis of studies addressing specific clinical questions. The relevant steps in writing a systematic review from the formulation of an initial research question to sensitivity analyses in conjunction with the combined analysis of the pooled data are described. Important issues that need to be considered when appraising a systematic review or meta-analysis are outlined. Some of the terms that are used in the reporting of systematic reviews and meta-analyses, such as relative risk, confidence interval, Forest plot or L'Abbé plot, will be introduced and explained.