An original analysis of Alfred C. Kinsey’s scientific career that uncovers the roots of his research methods. Donna J. Drucker describes how Kinsey’s enduring interest as an entomologist and biologist in the compilation and organization of mass data sets structured each of his classification projects. As she shows, Kinsey’s scientific rigor and his early use of data recording methods and observational studies were unparalleled in his field. Those practices shaped his entire career and produced a wellspring of new information, whether he was studying gall wasp wings, writing biology textbooks, tracing patterns of evolution, or developing a universal theory of human sexuality.