One pressing issue in libraries today is the censorship of information. This study applies Kurt Lewin's gatekeeping theory to examine the decision-makers as well as the different pressures and constraints that are at issue in decisions regarding challenges and censorship attempts that occur in public libraries. Through an in-depth case study of two federal court cases dealing with challenges and censorship attempts that occurred in public libraries, this study seeks to identify the gatekeeping structures present within public libraries, specifically those that contribute to conditions that encourage librarians to censor. A qualitative content analysis of court documents as well as newspaper articles covering the court cases being analyzed, followed by a series of interviews with individuals involved in the cases, seek to reveal in more complexity the gatekeeping structure present in public libraries. Knowing who the decision-makers, or gatekeepers, are in the decision-making process, whether it is library boards, library directors, or public officials, is crucial to the understanding of censorship in public libraries. Central to the study is the phenomenon of librarians themselves engaging in acts of censorship. Factors such as power and authority can lead librarians to engage in censorship activities as a reaction to instructions from their governing bodies. Without a clear understanding of the function of gates and gatekeepers in the decision-making process, libraries may allow unintended censorship of ideas and information to persist. This study seeks to inform librarians and information professionals to become better equipped to support the fight against censorship. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]