An extensive search of Medline and the Cochrane Library (any date up to December 31, 2010, restricted to randomized clinical trials, published in English) was performed for all trials containing, in any field, the words "sitagliptin," "vildagliptin," "saxagliptin," "alogliptin," "linagliptin," and/or "dutogliptin." Completed but unpublished trials were identified through a search of the ClinicalTrials.gov website, using the same keywords as above.