Group information repositories are systems for organizing and sharing files kept in a central location that all group members can access. These systems are often assumed to be tools for storage and control of files and their metadata, not tools for communication. The purpose of this research is to better understand user behavior in group information repositories, and to determine whether social factors might shape users' choices when labeling and organizing information. Through interviews with group information repository users and analysis of system log data, I found that users tend to restrict their activities in a repository to files they "own," are reluctant to delete files that could potentially be useful to others, dislike the clutter that results, and can become demotivated if no one views files they uploaded. I also conducted an online experiment in which participants labeled and organized short text files into a file-and-folder hierarchy, and later completed search tasks in the hierarchies created by others. Participants came from two intellectual communities, and were instructed to organize the files for one of three different audiences: themselves, someone from the same intellectual community, and someone from the other community. I found that when participants created hierarchies for an audience they imagined was like them, everyone searched more efficiently, regardless of whether they shared community membership with the hierarchy's creator. Further, analyses of the hierarchies showed that users performed better when file and folder labels were more similar to the text of the documents they represented. These results show that audience design, a communication process, can affect group information management tasks. The findings from both studies suggest that sharing files via a group information repository is more complicated than simply making them available on a server. Processes that affect spoken communication also impact word choices when the "interaction" is mediated by a repository. With this new knowledge, it is possible to begin design work on a new class of systems that go beyond mere storage, and better support the social aspects of user behavior in group information repositories. [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/en-US/products/dissertations/individuals.shtml.]