This study explored teachers' perspectives of AT use, effectiveness of AT, elements teachers' take into consideration when selecting AT, barriers, and resources needed for effective use of AT with students with severe intellectual and developmental disabilities. In order to answer this study's research questions, I employed a sequential explanatory mixed methods design. I conducted a self-administered online survey and online interviews to collect data from participants. This study consisted of two phases, quantitative followed by qualitative interviews. A total of 92 special education teachers from four special education institutes were surveyed, and five teachers in the second phase were interviewed to provide interpretations for the data analyzed from the first phase. Results demonstrated that there was a lack of AT use, with teachers reporting higher use of low-tech than mid-tech and high-tech. The most reported barriers were lack of AT devices, lack of funding, and lack of training. The results also demonstrated that there were statistical differences in the use of AT between the four special education institutes, teachers with AT training, and teachers' familiarity with AT. In the second, qualitative, phase, four major themes emerged from the interviews, as well as several sub-themes. The four themes were (a) the use of AT, (b) considerations, (c) barriers, and (d) professional development. These themes and sub-themes made it possible to interpret and elaborate on the data collected in the first, quantitative, phase. [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.]