ART has evolved over time and frozen-thawed embryo transfer (FET) is now a frequently performed, successful option. During the last decade, cryopreservation techniques have received considerable interest, whereas interest in the priming and preparation of the endometrium prior to and after embryo transfer was more limited. The available evidence for the rationale and timing of progesterone supplementation as well as an understanding of the differences among progesterone formulations with respect to efficacy, optimum use, and patient preference is worth examining. A Summit was convened to review the literature on progesterone supplementation in ART and after FET and to provide guidance on the most clinically relevant issues. Utilizing an innovative consensus-building model to examine the evidence, Summit faculty drafted summit statements prior to the meeting, completed a literature search, and created a presentation based on this. At the conclusion of their discussion the faculty developed final summit statements, evaluating the strength of the evidence supporting each statement, and rating their level of support for each statement. The clinically relevant topic areas were the rationale for progesterone supplementation, timing and appropriate dosing, whether progesterone sérum levels reflect outcomes, and distinguishing among progesterone formulations with respect to efficacy, tolerability, and patient preference/satisfaction.