The "Connected Mathematics Project" ("CMP)" is a problem-centered mathematics curriculum designed for all students in grades 6-8. Each grade level of the curriculum is a full-year program and covers numbers, algebra, geometry/measurement, probability, and statistics. The program seeks to make connections within mathematics, between mathematics and other subject areas, and to the real world. The curriculum is divided into a sequenced set of units, each organized around different mathematical topics. The four to seven lessons in a unit each contain one to five problems that the teacher and students explore in class. Additional problem sets, called Applications, Connections, and Extensions, in each lesson help students practice, apply, connect, and extend their understanding and skills. Each lesson culminates in a Mathematical Reflections activity. According to the developers, the "CMP" addresses National Council of Teachers of Mathematics standards. Three studies of the "CMP" met the What Works Clearinghouse (WWC) evidence standards with reservations. The three studies included over 26,000 students from grades 6-8 in about 100 schools located in northeastern, south central, midwestern, and western states. The "CMP" curriculum was found to have mixed effects on math achievement. (Contains 8 tables and 9 footnotes.) [This publication was produced by the What Works Clearinghouse. The following studies are reviewed in this intervention report: (1) Ridgway, J. E., Zawojewski, J. S., Hoover, M. N., & Lambdin, D. V. (2002). Student attainment in the Connected Mathematics curriculum. In S. L. Senk & D. R. Thompson (Eds.), "Standards-based school mathematics curricula: What are they? What do students learn?" (pp. 193-224). Mahwah, NJ: Lawrence Erlbaum Associates, Inc.; (2) Riordan, J. E., & Noyce, P. E. (2001). The impact of two standards-based mathematics curricula on student achievement in Massachusetts. "Journal for Research in Mathematics Education," 32(4), 368-398; and (3) Schneider, C. L. (2000). Connected Mathematics and the Texas Assessment of Academic Skills. "Dissertation Abstracts International," 62(02), 503A. (UMI No. 3004373).]