"SRA Real Math Building Blocks PreK" (also referred to as "Building Blocks for Math") is a supplemental mathematics curriculum designed to develop preschool children's early mathematical knowledge through various individual and small- and large-group activities. It uses "Building Blocks for Math PreK" software, manipulatives, and print material. "Building Blocks for Math" embeds mathematical learning in children's daily activities, ranging from designated math activities to circle and story time, with the goal of helping children relate their informal math knowledge to more formal mathematical concepts. Two studies of "Building Blocks for Math" met the What Works Clearinghouse (WWC) evidence standards. They included over 250 preschool children from New York State. This report focuses on immediate posttest findings to determine the effectiveness of the intervention. The WWC considers the extent of evidence for "Building Blocks for Math" to be small for mathematics achievement. No studies that met WWC evidence standards with or without reservations addressed oral language, print knowledge, phonological processing, early reading/writing, or cognition. "Building Blocks for Math" was found to have positive effects on mathematics achievement. (Contains 8 footnotes.) [The following two studies are reviewed in this intervention report: (1) Clements, D. H., & Sarama, J. (2006, June). "Scaling up the implementation of a pre-Kindergarten mathematics curriculum: The Building Blocks curriculum." Paper presented at the Institute of Education Sciences Research Conference, Washington, D.C.; and (2) Clements, D. H., & Sarama, J. (2007). "Effects of a preschool mathematics curriculum: Summative research on the Building Blocks project." Journal for Research in Mathematics Education, 38(2), 136-163.]