This exploratory case study examines how three media attributes in 3-D MUVEs--avatars, 3-D spaces and bubble dialogue boxes--affect interaction in an online problem-based learning (PBL) activity. The study participants were eleven undergraduate students enrolled in a 200-level, three-credit-hour technology integration course at a Midwestern university. Other participants include a course instructor and online facilitator. The findings of this study indicate that the avatar, 3-D space and bubble dialogue box attributes in "Second Life" affect online interaction in all PBL stages with varied outcomes. This study finds that the avatar attribute personalizes interaction and sustains engagement, motivation, social presence and teaching presence. This study, however, finds that a major disadvantage of the avatar attribute is that it could distract participants from focusing on discussions. The 3-D space attribute supports cognitive presence by providing learning venues, such as small and large-group meeting spaces. It also supports teaching presence when it sets the climate for learning by providing separate group meeting spaces and a visual display for large-group sharing. A disadvantage of this attribute, however, is that in some instances, it allows intrusions by non-participants. In addition, the 3-D space makes it difficult for participants to gather and share resources because they have to rely on external tools, such as e-mail, to share information with group members. The bubble dialogue box attribute provides a comic-book style interaction to visually display text that allows participants to brainstorm ideas and keep track of discussions in small group settings. The comic-book aspect of the bubble dialogue box attribute could support social, cognitive and teaching presence. This study, however, finds that the bubble dialogue attribute may not be as effective in large group settings because the text fades away quickly and it blocks avatars' views of presentation screens. Other findings of this study indicate that the learning process can be hampered by issues related to system requirements, the adaptability of "Second Life's" interface and open access in "Second Life." Based on this study's findings, several recommendations for practice and future research are provided. [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.]