Arthur B. Powell and Marilyn Frankenstein's new book, Ethnomathematics: Challenging Eurocentrism in Mathematics Education, illuminates for our consideration a body of very practical mathematical knowledge largely discounted in the traditional mathematical community when compared with the abstract, theoretical mathematical knowledge typically valued highly by mathematicians. Ethnomathematics has caused us to call into question which mathematical knowledge really counts and thus has come to signify more than just “the study of mathematical ideas of nonliterate peoples” (a definition first offered by Marcia and Robert Ascher in the early 1980s in their paper, “Ethnomathematics,” reprinted as chapter 2 of this volume, p. 26). Editors Powell and Frankenstein use, instead, the broader definition of ethnomathematics provided in the book's opening chapter, “Ethnomathematics and Its Place in the History and Pedagogy of Mathematics,” by Ubiratan D'Ambrosio, a Brazilian mathematics educator whom many consider the intellectual progenitor of ethnomathematics. D'Ambrosio defines ethnomathematics as the mathematics that all cultural groups engage in, including “national tribal societies, labor groups, children of a certain age bracket, professional classes, and so on” (p. 16). Each group, including mathematicians, has its own mathematics. From D'Ambrosio's perspective, ethnomathematics exists at the confluence of the history of mathematics and cultural anthropology, overcoming the Egyptian/Greek differentiation between practical and academic mathematics.