Writers for both academic and popular audiences often use the term "gender" when considering differences between the educational experiences of male and female students, and the distinction often appears to be based on a traditional understanding of the term "sex". The authors of this article argue that "gender" and "sex" should be distinguished more clearly in education research and that the pattern of unclear, conflated, and even synonymous use of the terms has slowed progress in understanding how gender influences students' educational experiences. The authors present evidence of conflated use, review the wide diversity in orienting perspectives and definitions of "gender", show how current American Psychological Association publication guidelines fail to provide clear guidance on the use of the terms, and make recommendations for improving research practice. (Contains 8 notes.)