This qualitative case study explored how course context, such as course design, facilitation, and community, supports students' basic psychological needs and thus shapes their situational motivation to participate in asynchronous online discussions in different course contexts. Three upper-level undergraduate courses in different disciplines were investigated. All three courses were fully online courses and utilized asynchronous online discussion as one of the regular class activities. However, most students were on-campus students who took online courses for flexibility. There were a few distance learners in one of the courses. This study was conducted in a natural setting without any intervention to control the course events. Instead, interview, participation diaries, discussion archives, and surveys were used to collect data. For each course, four to six students participated in the interviews and created participation diaries. The instructors and the TAs were also invited to be interviewed before and after the five weeks of discussions. Each course was analyzed separately to obtain individual findings within a specific course context including course design, facilitation, and community. Each course used a different approach for the weekly discussion activities. The first case used project-based discussion, the second case used topic-based discussion, and the third case used problem-based discussion. For these tasks with different discussion designs, facilitation strategies, and peer interaction, students from each case shared different perspectives regarding their satisfaction of needs and situational motivation to participate in online discussions actively and passively. A cross-case comparison provided a local theory and implications regarding instructional design to maximize students' situational motivation to participate in online discussions. When students' basic needs for autonomy, competence, and relatedness were met, the quality of participation increased because students exerted more effort and time into writing quality posts. The increased quality of posts enhanced students' passive participation to learn more from others. Their basic needs were primarily supported by the discussion design and instructor's facilitation. However, students' participation is extrinsic in general because they have to participate both actively and passively to meet the requirements. Therefore, both the quantity and quality of participation can be shaped through situational motivation generated by the discussion design and instructor facilitation. When a course is challenging, the need for competence through the instructor's guidance and support increases, and the need for relatedness to help each other elevate their competence also increases. Although situational motivation within the course context is critical, students' motivation to participate resulted from the interplay between personal traits and environmental factors within the course context. This means that different types of motivations interplay at various levels and generate students' motivation to participate both actively and passively. For example, when students' basic needs were met, students' personal goal orientation became salient because some students needed more justification for extra effort. When a course is difficult, students' self-regulation skills or prior knowledge become a critical factor in their active participation and satisfaction. Overall, this case study added to previous findings about course design factors affecting participation by answering the "how" question instead of the "what" question which was the focus of most previous studies. This study also provided some answers about the "reasons" behind the intertwined relationships between the course elements, needs satisfaction, and learner motivation instead of focusing on the relationships themselves. [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.]