The Individuals with Disabilities Act mandates that all students with or without disabilities should be included in the regular education classroom to the greatest extent appropriate. Research shows the importance of the principal's ability to shape programs, policies and school cultures that are supportive of inclusion. Deploying a modified version of the Principals and Inclusion Survey (PIS) developed by Praisner (2000), this study examined the attitudes, beliefs and behaviors of elementary principals in the state of Pennsylvania regarding inclusion and two inclusive instructional practices, co-teaching and differentiated instruction. Findings compared the responses of principals representing the top 20% of school districts practicing the highest percentage of inclusion of students with disabilities into the regular education classroom (as measured by the state's Least Restrictive Environment Index) with those of the bottom 20% of school districts practicing the least percentage of inclusion. The objective was to investigate any association of the principals' self-reported support for inclusion and inclusive practices with their ranking on the Pennsylvania's Least Restrictive Environment Index. Findings concluded there was no statistically significant difference in the responses of the two groups in most areas. Overall, principals of both groups scored favorably regarding their attitudes and behaviors in support of inclusion, co-teaching and differentiated instruction. Both groups reported high percentages of teachers employing co-teaching and differentiated instruction. The greatest limitation of this study is the relatively small sample size, making it difficult to generalize any findings. There is, however, evidence to suggest that the attitudes and practices of elementary principals in Pennsylvania regarding inclusion are more favorable than previously documented. In addition, two promising inclusive instructional practices (co-teaching and differentiated instruction) are purportedly being embraced by these same principals. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]