The purpose of this dissertation research study was to explore instructors' perceptions of the educational application of three-dimensional (3D) virtual worlds in a variety of academic discipline areas and to assess the strengths and limitations this virtual environment presents for teaching adult learners. The guiding research question for this dissertation study was: What are instructors' perceptions of the strengths and limitations of three-dimensional virtual worlds as learning spaces for teaching adult learners? The following four questions supported this research: (a) How do instructors implement educational experiences in 3D virtual worlds, for adult learners? (b) How do instructors facilitate adult learning in 3D virtual worlds across disciplines? (c) What insights do instructors describe about the adult learners' needs in this virtual environment? and (d) How do instructors describe a successful immersive learning experience implemented in a 3D virtual world? This dissertation research study was conducted as a heuristic case study with instructors interviewed from multiple locations that taught in private and public institutions of higher education in the southeastern United States. Instructors were asked to reflect on their experiences teaching in a virtual world, and to describe their perceptions of characteristics of a successful virtual world implementation in their teaching practice. The study found instructors perceived the benefits of learning in 3D virtual worlds for adult learners as the ability to experience content, community, collective wisdom, immersion, authentic learning, and a "sense of academic home" in an online environment. The study found assessment methods are uniquely situated to take advantage of the attributes of 3D virtual worlds, the social learning made possible, and the digital artifacts this space affords. The dissertation concludes with recommendations for faculty and higher education administrators that address the significant practice, policy, and institutional issues and concerns that arise with the application of virtual worlds as an instructional learning space. [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.]