This article describes a study of the two most popular plagiarism-detection software platforms available on today's market--Turnitin (http://www.turnitin.com/static/index.html) and SafeAssign (http://www.safeassign.com/). After a brief discussion of plagiarism's relevance to librarians, the authors examine plagiarism-detection methodology and conduct a review of the current literature regarding plagiarism-detection efficacy. To evaluate detection efficacy for Turnitin and SafeAssign, the authors constructed a brief study in which twenty sample papers containing portions of plagiarized material were submitted to each platform. The results show that Turnitin had the highest overall success at plagiarism detection with an 82.4 percent detection rate. Additionally, both platforms had a combined false-positive detection rate of 16.8 percent. The authors conclude that close review of material suspected of plagiarism is still essential for proper identification. (Contains 4 tables and 1 figure.)