The purpose of this study was to synthesize research on the effects of interventions to improve the mathematics achievement of students considered low achieving or at risk for failure. Meta-analytic techniques were used to calculate mean effect sizes for 15 studies that met inclusion criteria. Studies were coded according to 5 categories of mathematics interventions, and effect sizes were examined on a study-by-study basis within each of these categories. Results indicated that different types of interventions led to improvements in the mathematics achievement of students experiencing mathematics difficulty, including the following: (a) providing teachers and students with data on student performance; (b) using peers as tutors or instructional guides; (c) providing clear, specific feedback to parents on their children's mathematics success; and (d) using principles of explicit instruction in teaching math concepts and procedures.