This research brief discusses some of the fundamentals of quality program implementation that have been identified through research and practice and that may be useful for practitioners and researchers alike. The brief defines quality program implementation, and highlights the importance of a high quality implementation, identifies 23 factors that affect implementation, discusses 14 steps in achieving quality implementation (10 of which need to occur before a program starts), and notes that responsibility for quality implementation is shared by key stakeholders. The factors that can affect implementation quality range from societal, community, program, practitioners, and organizational influences, as well as the implementation process itself. The brief explains how implementation should focus on core components, allowing adaptation of other aspects to suit the population and setting. This is one of four research briefs prepared under the auspices of an ASPE contract entitled Emphasizing Evidence-Based Programs for Children and Youth: An Examination of Policy Issues and Practice Dilemmas Across Federal Initiatives.