The problem addressed in this study was that regular education teachers lacked the training to include students with disabilities in inclusive classrooms. The evidence indicated that teachers were beginning to show greater levels of frustration, students were being referred out of the classroom, and many students were being sent to the special education classroom. Three research questions evolved from the problem statement: 1) Will the teachers' knowledge of best practices in inclusive classroom increase from pretest to posttest, as measured by the Inclusion Knowledge Test? 2) Will teachers' perceptions on inclusive classrooms change from preimplementation to postimplementation, as measured by the scores on the Teachers' Attitude Toward Inclusion Survey? 3) What will be the teachers' perceptions of inclusion practices based on the professional-development training? The three research questions were aligned with the Inclusion Knowledge Test, the Teachers' Attitude Toward Inclusion Survey, and the Teachers' Inclusion Professional-Development Module interview instrument. The first instrument was used to collect data for Research Question 1, the second instrument was used to collect data for Research Question 2, and the third instrument was used to collect data for Research Question 3. The intervention involved an inclusion professional-development model, with six of the Halvorsen and Neary (2009) modules implemented during a 9-week treatment period. The total exposure time of the 19 teachers to the treatment was 27 hours. The single-group, pretest-posttest research design was the guide for data collection and data analysis for Research Questions 1 and 2. The descriptive-interview research design served as the guide for Research Question 3. Ten randomly selected teachers also participated in one-on-one interviews. Quantitative data for Research Questions 1 and 2 were analyzed with statistical software. Descriptive statistics calculated were pretest and posttest means, standard deviations, and effect sizes. The inferential-statistical model for Research Questions 1 and 2 was the t test for paired samples. Qualitative data for Research Question 3 were categorized and summarized, and the summaries were used to respond to the research question. The findings for Research Question 1 showed that teachers' knowledge of best practices in inclusive classrooms increased from pretest to posttest, and the increase had statistical and practical significance. The findings for Research Question 2 showed that teachers' perception scores on inclusive classrooms increased from pretest to posttest, and the increase had statistical and practical significance. The findings for Research Question 3 indicated that the intervention was successful in preparing teachers to teach in inclusive classrooms. Limitations were discussed, as well as recommendations for future studies. [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.]