A systematic review synthesizes findings across multiple population-based studies. It applies the same level of scientific rigor to the review process as used when conducting primary research. It uses the scientific method so that reviews are transparent, reproducible, and objective, thereby reducing the likelihood of bias and random error in the summarization process. Systematic reviews that follow this method and are appraised to have validity (the extent to which their design and conduct are likely to have been protected from bias) are a quality source of evidence to the practitioner and policy maker and are replacing primary research as the source of evidence on which decisions are based. This chapter describes the purpose of a systematic review and the steps in performing such a review. It highlights the benefits of systematic reviews as compared to traditional narrative reviews.