Underrepresentation of women in economics is documented in many studies. Investigation of its sources at the undergraduate level is examined through students' decisions to persist in economics, either beyond an introductory course or in their major choices. The authors add to the literature by analyzing students' decisions to take their first introductory economics course, an intermediate theory course, and ultimately major in economics, using the Multiple-Institution Database for Investigating Engineering Longitudinal Development. Results indicate that a smaller percentage of women take economics at all levels--introductory courses, theory courses, and majoring in economics. Even after controlling for aptitude, demographic characteristics, prior interest, course performance, environment, and course timing, persistent gender differences in the likelihood of partaking in economic education beyond the introductory course decision endure. (Contains 9 notes and 5 tables.)