Twenty-five years have elapsed since the publication of Benjamin S. Bloom's article titled "Learning for Mastery." With approximately 2,000 master learning/testing citations in the ERIC data base alone, Bloom's 1968 piece is indeed one of the most generative works to appear in the educational psychology literature in decades. At this quarter-century juncture, then, it is appropriate to reflect retrospectively and prospectively on the meaning, impact, and continuing possibilities of Bloom's learning for mastery. In so doing, this paper focuses on what could be termed the "internationalization" of mastery learning. Evidence of mastery learning research and development initiatives in well over 30 nations does indeed invite not only an analysis of what has already transpired in the worldwide community but also a projection of future directions for mastery learning in the international arena. (Contains 119 references.) (Author)