Thesis (Ed.D.)--Boston University / This study aimed at refining one of the most influential and well-known theories of distance education - the theory of transactional distance (TD). TD theory was developed by Michael G. Moore based on correspondence forms of distance education. The study researched a distance learning environment that had not been investigated in relation to TD - synchronous Web-extended classrooms. In this unique format, live on- campus classes are delivered simultaneously to both in-class students on campus and remote students on the Web who attend synchronously via virtual classroom Web collaboration software. The research involved N=235 students enrolled in 14 graduate business courses. ANOVA tests, correlation and regression analyses were deployed on the 46-item "Scale of TD for synchronous Web-extended learning environments" questionnaire. The study compared perceived TD for three attendance groups: always in-class, always online, and mixed. It found no difference in TD among them. The learning environment enabled by using Saba-Centra Web collaboration software combined with other technologies provided a comparable learning experience for all three learner groups. The findings confirmed that four dimensions of dialogue, student-student, student-instructor, student-content, and student-interface interactions are significant in students' perceived TD and their engagement with learning. Moreover, their significance levels varied for different attendance groups. This research confirms the need to refine TD theory to view dialogue as a multidimensional construct. Furthermore, student-instructor and student-student interactions were significant factors that affected TD in all three learner groups. This study analyzed student satisfaction. The study not only found no difference in satisfaction by attendance type, but also it found that TD is strongly related to student satisfaction: the lower the TD, the more satisfied the students are with the learning environment, including interactions with the instructor, fellow students, course content, and the interface. For all attendance groups, interaction with other students was the common factor that affected satisfaction. The study demonstrated that the level of TD also affects students' perceived learning: the lower the TD, the higher the students' perceived learning. Thus, the study suggests that instructors plan activities that include interpersonal interactions between themselves and students, and also among students in all attendance groups.