This article is based on "Freeze-Thaw Durability of SRWs: Lessons Learned," presented by Robert Thomas, director of research for the National Concrete Masonry Association, at Masonry Expo '98. Since the mid- to late-1980s, concrete block producers have seen sales of segmental retaining wall (SRW) units increase dramatically. SRW units are more susceptible to freeze-thaw damage than are standard block. Although in-service SRW units show little evidence of freeze-thaw deterioration, the National Concrete Masonry Association is looking for more data showing which factors improve freeze-thaw durability to meet ASTM C 1262, "Evaluating the Freeze-Thaw Durability of Manufactured Concrete Units and Related Concrete Units." Factors affecting durability are aggregates, cement content, admixtures and water content. KEYWORDS: SRW, retaining, wall, freeze-thaw