This monograph complements volume 36, issue number 4 of ASHE Higher Education Report: "Understanding the New Majority of Non-Tenure-Track Faculty," and focuses on theories applied to study non-tenure-track faculty and philosophical and practical tensions represented in the literature. The chapter "Theories Used to Study and Understand Non-Tenure-Track Faculty" reviews theories applied to the study of these faculty. The following chapter, "Tensions," examines the various conflicts that arise in ideology, practice, and empirical research regarding non-tenure-track faculty and their role in the academy. It begins with a discussion of the role of non-tenure-track faculty in relation to tenure and then discusses the tension in the two-tier system between tenure-track and non-tenure-track faculty, and competing interests. Both theories and tensions examine underlying beliefs and assumptions critical for shaping policy and conceptualizing research. The chapter focuses on these underlying beliefs as they have remained tacit and, the authors argue, have negatively affected current policies for non-tenure-track faculty. By making these assumptions explicit, the authors hope to change the nature of the dialogue and resulting policies. The chapter ends with a review of the research on productivity, cost-effectiveness, student outcomes, and the effects of the rising number of non-tenure-track faculty, systematically addressing various tensions in the literature that have not been brought together and examined as a whole. More productive policymaking regarding non-tenure-track faculty will likely be facilitated with productive discussion and understanding of this group. The final chapter, "Conclusion and Suggestions for Further Research," offers conclusions related to research from earlier chapters and provides ideas for future research. The authors' meta-analysis relies heavily on three comprehensive studies: (1) "The Invisible Faculty: Improving the Status of Part-Timers in Higher Education" (Gappa and Leslie, 1993), focused exclusively on part-time faculty; (2) "Teaching Without Tenure" (Baldwin and Chronister, 2001), focused on full-time non-tenure-track faculty; and (3) "Making the Best of Both Worlds" (Hollenshead and others, 2007), which is the only national study looking at all non-tenure-track faculty in four-year institutions. "The Invisible Faculty" is a qualitative case study of multiple institutions examining policies and practices related to part-time faculty--hiring, salary, benefits, governance. Gappa and Leslie interviewed administrators and tenure-track faculty about their views of part-time faculty and talked to part-time faculty about their experiences. "Teaching Without Tenure" is also a qualitative case study of multiple institutions examining policies and practices related to full-time non-tenure-track faculty. It was the first major study to focus on this growing population. The book ranges in topics from the history and reasons for growth to reports about policies and practices used on campuses to a report of the experiences of full-time non-tenure-track faculty. "Making the Best of Both Worlds" is a national quantitative study of approximately 500 institutions asking administrators about their deployment, policies, and practices relative to both part-time and full-time non-tenure-track faculty. It is one of the few studies to disaggregate these groups in studies and examine differences in policy. (Contains 2 notes and name and subject indexes.)