This report summarizes the methodology, measures, and findings of research on the influence on student achievement outcomes of K-12 online and blended face-to-face and online learning programs that offer differentiated learning options. The report also describes the characteristics of the learning programs. Most of the examined programs used blended learning strategies, and all the examined programs offered some means to differentiate their content, difficulty level, or pacing. Some 45 percent of the blended learning programs studied (5 of 11) offered differentiation in the face-to-face component of instruction. In some of the most rigorous studies, statistically significant positive effects were found for four blended learning programs: Cognitive Tutor Algebra I, LeapTrack, READ 180, and Time To Know. This study addressed two research questions: (1) What are the characteristics of online and blended learning programs that offer differentiated learning options to K-12 students in the United States and that have been the subject of research?; and (2) What are the methodologies, measures, findings, and strength of evidence of studies that have examined these programs using randomized controlled trials, quasi-experimental, or correlational research designs? To answer these questions, the study team searched research journal databases, research organizations' websites, and the websites of online and blended learning program vendors to identify relevant studies. Studies were included only if they focused on online or blended learning programs that offered differentiated learning options. Programs were included regardless of whether they were used to provide a full curriculum (including content for a semester or yearlong course) or to supplement an existing course curriculum. The following are appended: (1) Literature search procedures; and (2) Online and blended learning programs and research studies included in the literature summary.