Supplementary cementitious materials (SCMs) are commonly used in concrete mixtures as a replacement of a portion of clinker in cement or as a replacement of a portion of cement in concrete.This practice is favorable to the industry, generally resulting in concrete with lower cost, lower environmental impact, higher long-term strength, and improved long-term durability.SCMs have been used in Portland cement concrete for decades and many of their effects are well-understood.Most recent research on SCMs has focused on a few areas:exploring new materials, iacreasing replacement amounts, developing better test methods, treating or modifying materials, and using additives (e.g.limestone or nanosilica) to improve performance.The advances in knowledge provided by research in these areas are reviewed in this paper, emphasizing the impact of the research on the field.