This master thesis serves to investigate how collaborative learning can be facilitated in 3D virtual environments. The objective was to see how 3D virtual worlds could be applied when conducting collaborative learning, both formal and informal. I was also interested in reflection as a part of collaborative learning processes, and chose to integrate this into my research questions: 1. How can 3D virtual worlds, like SecondLife, facilitate collaborative learning? 2. How can one use virtual worlds for collaborative learning-purposes in both formal and informal learning situations? 3. In what way can reflection be beneficial to collaborative learning in virtual worlds? SecondLife is a widely used 3D virtual world, utilized in a variety of learning situations. Its design and layout seem conducive to creating spaces that facilitate collaboration, and supports both formal and informal learning. I have used a variety of theoretical frameworks and perspectives to structure the thesis, and form the basis for the discussions and conclusions. I have utilized constructivist learning theory to describe the collaborative learning facilitated through virtual environments. This is due to the generous focus on collaboration and team-work throughout this thesis. As collaborative-learning situations enable the creation of shared practices and understanding, I will discuss the perspectives surrounding communities of practice, first coined by Lave and Wenger (Wenger 2000). Computer-supported collaborative learning is a perspective that serves to integrate technology and learning, and I have relied on this to contextualize the examples used, the CAMO-project being one of them. Its objective was to create cultural awareness in military operations, through collaborative simulations in a virtual Afghan village. The other example involved nursing students, who practiced communication skills with fatally ill patients and their relatives. Both examples highlights the opportunities for collaborative learning in virtual environments. Taking advantage of new technology for learning purposes, could create new possibilities for learning, maybe particularly collaborative learning. This is an important topic, as it could facilitate better and more motivating learning methods. Research Method and Data Analysis As this thesis is a qualitative Meta study, I relied on interviewing as my main data collecting method. I interviewed three practitioners within the field of technology and learning. They had earlier collaborated as facilitators in the CAMO-project, and also possessed a variety of experiences with 3D virtual worlds and learning. The data collected was analyzed and categorized through an iterative process. I worked with the transcribed interviews and notes, in several stages to analyze and attain the best categorizations for the data gathered. These five categories included: 1. SecondLife as a Learning Environment, 2. Comparison Between Different 3D Virtual Worlds, 3. Collaborative Learning, 4. Formal and Informal Learning and 5.Dialogue and Reflection. These categories helped me present the most valuable data andformed the basis for the discussion. Findings and Main Conclusions The informants and the theoretical framework both supported 3D virtual worlds and the opportunities within these platforms to contain great potential for collaborative work. As collaborative learning requires participants to socially interact and communicate with each other, the suitability relies on the communication options and features within the learning platform. SecondLife and other 3D virtual worlds are often created to serve as arenas for socialization, they are therefore well equipped with the necessary communication tools. To facilitate both formal and informal learning there are aspects that need to be present. Within 3D virtual worlds there needs to be possibilities to plan and design formally structured exercises, as well as unstructured informal activities. The informants were generally favorable to utilizing virtual environments for informal learning purposes, but disagreed on the formal learning possibilities. However, there are numerous examples of 3D virtual worlds being utilized for formal learning practices, and all the informants have had positive experiences with lectures and seminars conducted virtually. Reflective practice, most notably known through the work of Donald. A. Schön, proposes the importance of dialogues and reflection sessions, for participants in collaborative learning activities (Schön, 1983). This was a major part of the CAMO-project, and enabled the participants to express, challenge and reflect on the learning experience. The informants were unanimous in their perceived importance of reflection, to attain the most valuable learning outcome. They saw this as an important aspect of collaborative learning.