Given the tremendous proliferation of student plagiarism involving the Internet, the purpose of this study is to determine which theory of ethical reasoning students invoke when defending their transgressions: deontology, utilitarianism, rational self-interest, Machiavellianism, cultural relativism, or situational ethics. Understanding which theory of ethical reasoning students employ is critical, as preemptive steps can be taken by faculty to counteract this reasoning and prevent plagiarism. Additionally, it has been demonstrated that unethical behavior in school can lead to unethical behavior in business; (...) therefore, correcting unethical behavior in school can have a positive impact on organizational ethics. To meet this objective, a content analysis was conducted on the written records of students formally charged with plagiarizing at a large West Coast university. Each case was classified according to the primary ethical reasoning that the student used to justify plagiarism. Results indicate that students predominately invoke deontology, situational ethics, and Machiavellianism. Based on these findings, specific recommendations are offered to curb plagiarism. (shrink)