This article focuses on the research program on mathematical problem solving conducted by the Center on Accelerating Student Learning (CASL). First, a subset of CASL themes, illustrated in the mathematical problem-solving studies, is highlighted. Then, the theoretical underpinnings of the mathematical problem-solving intervention methods are described, along with a brief overview of prior research. Next, the problem-solving dependent measures are presented, with explanation of how these measures explore a range of transfer distances that extend to real-life problem-solving situations. Then, to illustrate the research program, 3 intervention studies are described. The article concludes with recommendations for practice and future study.