To provide guidance to obstetricians and gynecologists for using findings from metaanalyses in clinical practice, we describe the principles and methods of metaanalysis, including its strengths and weaknesses. Then we illustrate these principles by reviewing four metaanalyses published recently in the American Journal of Obstetrics and Gynecology by using a systematic approach to evaluation based on 15 questions. In these published metaanalyses most of the questions are addressed, but we noted an absence of attention to coding aspects in all studies. The usefulness of metaanalysis largely depends on the quality of the studies that are synthesized, the conduct of the metaanalysis, and the reporting of the methods and results. Proper use of metaanalyses requires an understanding of the strengths and weaknesses of the method and attention to the manner of reporting. The principles of metaanalysis are not complex, and the potential benefits can be enormous for patient care.