Tremendous gains have been made in the prevention of mother-to-child HIV transmission (PMTCT) in sub-Saharan Africa. Ambitious goals for the "virtual elimination" of pediatric HIV appear increasingly feasible, driven by new scientific advances, forward-thinking health policy, and substantial donor investment. To fulfill this promise, however, rapid and effective implementation of evidence-based practices must be brought to scale across a diversity of settings. The discipline of implementation research can facilitate this translation from policy into practice; however, to date, its core principles and frameworks have been inconsistently applied in the field. We reviewed the recent developments in implementation research across each of the four "prongs" of a comprehensive PMTCT approach. While significant progress continues to be made, a greater emphasis on context, fidelity, and scalability-in the design and dissemination of study results-would greatly enhance current efforts and provide the necessary foundation for future evidence-based programs.