Time and timeliness are key issues in appraising and ensuring the clinical relevance of systematic reviews. Time considerations entering the systematic review process include the history of the clinical problem, disease, or treatment that is the target of the review, and the history of the research conducted to address it. These considerations guide: (i) formulation of the research problems and questions; (ii) setting of parameters for the search and retrieval of studies; (iii) determination of inclusion and exclusion criteria; (iv) appraisal of the clinical relevance of findings; (v) selection of the findings that will be synthesized; and (vi) interpretation of the results of that synthesis.