This report presents results from the Ready To Learn Prekindergarten Transmedia Mathematics Study, a principal part of the summative evaluation of Ready To Learn, which is a partnership between the US Department of Education, the Corporation for Public Broadcasting, and PBS. Researchers found that preschool children who experienced a PBS KIDS Transmedia Math Supplement developed essential early mathematics skills. The PBS KIDS Transmedia Math Supplement was centered around public media videos and digital games, played on a selected set of learning technologies (interactive whiteboards and laptop computers). The important skills measured--counting; subitizing; recognizing numerals; recognizing, composing, and representing shapes; and patterning--increased significantly for the study's four- and five-year-old children, who were from traditionally economically disadvantaged communities where children are often less prepared for kindergarten than are their more socially and economically advantaged peers. Also important, preschool teachers who enacted the PBS KIDS Transmedia Math Supplement reported significant changes in their confidence and comfort with early mathematics concepts and teaching with technology. (author abstract)