"Connected Mathematics Project" (CMP) is a math curriculum for students in grades 6-8. It uses interactive problems and everyday situations to explore mathematical ideas, with a goal of fostering a problem-centered, inquiry-based learning environment. At each grade level, the curriculum covers numbers, algebra, geometry/measurement, probability, and statistics. The What Works Clearinghouse (WWC) identified two studies of CMP that both fall within the scope of the Primary Mathematics topic area and meet WWC group design standards. No studies meet WWC group design standards without reservations; the two studies meet WWC group design standards with reservations. Together, these studies included 3,062 students in grades 6-8 in at least 23 schools in 10 locations. The WWC considers the extent of evidence for CMP on the mathematics achievement of students in primary mathematics courses to be medium to large for the mathematics achievement domain, the only domain examined for studies reviewed under the Primary Mathematics topic area. CMP was found to have no discernible effects on mathematics achievement for students in primary mathematics courses. Appended to this report are the following: (1) Research details for Cai et al. (2011) (see EJ938481) ; (2) Outcome measures for the mathematics achievement domain; (3) Findings included in the rating for the mathematics achievement domain; and (4) Description of supplemental findings for the mathematics achievement domain. End notes, Recommended Citation, WWC Rating Criteria, and a Glossary of terms are also provided.