Using undergraduate student records from six large public universities from 1990 to 2003, the authors analyze the characteristics and performance of students by major in two economics courses: Principles of Microeconomics and Intermediate Microeconomics. This article documents important differences across students by major in the principles course and compares these students to those who graduate with a major in economics. The data indicate that about two thirds of students who graduate with a major in economics declared their major sometime after completing the Principles of Microeconomics course. The article documents differences in characteristics and performance for economics graduates who started as engineering, math, or physics majors as compared to business or economics majors. The authors also examine whether starting in one of the more math-intensive majors of engineering, math, or physics improves student performance in intermediate microeconomics if performance in the principles course was good. (Contains 3 tables.)