Why aren't more women pursuing careers in science, engineering, and math? Is the lack of women in these fields a consequence of societal discouragements, innate differences in ability between the sexes, or differences in aspirations? These questions always spark a host of other questions - and a multiplicity of answers - all of which have important implications for gender equality and for retaining the nation's competitiveness in the technological marketplace. The most reliable and current knowledge about women's participation in science is presented in this collection of fifteen essays written by top researchers on gender differences in ability. The essayists were chosen to reflect the diversity and complexity of views on the topic, about which knowledge has been accumulating and evolving for decades. The editors provide an introduction that defines the key issues and embeds them in historical context and a conclusion that synthesizes and integrates the disparate views. Written accessibly to appeal to students and non-specialists as well as psychologists and other social scientists, the contributors reframe this key controversy and challenge readers' emotional and political biases through solid empirical science. Taken together, the introduction, essays, and conclusion make a convincing case that sex differences are neither as unambiguous as earlier researchers suggested nor as insubstantial as some current critics claim. Sex differences in career choices are definitely not inevitable, as the past thirty years have documented both a sea change in the gender makeup of various fields and fluctuations in ability-score differences between the sexes. However, as the essays make clear, such changes leave open the possibility of cultural and biological bases for today's sex differences in science, engineering, and math participation.