Two studies addressed students' motivation and participation in an online discussion board which was part of a traditional lecture-based course. The discussion board represented an external communication resource to extend the learning activities beyond the classroom. Self-Determination Theory was used as the theoretical framework to investigate: (a) how students' participation in online discussion related to their intrinsic motivation and attitude toward the class; b) how students' intrinsic motivation changed over time; and c) what factors students noted as responsible for the changes in their motivation level. A total of 123 undergraduate students participated in online discussion as a normal part of their instructional technology class. The results showed that students' participation was related to their intrinsic motivation, but not to their computer/internet skills. Over time, students' intrinsic motivation for participating in online discussion dropped steadily. Student-reported reasons for the motivation changes are discussed. (Contains 2 figures and 4 tables.)