The Indicators of Successful Inclusion Scale (ISIS) was developed to measure pre-service and practicing educators' beliefs regarding factors that contribute to educating students with disabilities in general education classrooms. The measure was designed to assess teachers' beliefs and attitudes related to inclusive education and to consider their possible utility for understanding teachers' inclusion-related intentions and behaviors. Specifically, the ISIS targets personal and ecological factors thought to influence intentional inclusive practice: beliefs related to the perceived benefits of inclusion, beliefs regarding administrative school support for the practice of inclusion. ISIS scale development, and exploratory and confirmatory factor analyses yielded discrete subscales addressing teachers' ecological beliefs. Analyses of internal consistency and test-retest reliability data suggest the ISIS functions in a reliable fashion. Our construct validation procedures yielded evidence supporting the ISIS as a measure of pre-service and practicing teacher beliefs pertaining to inclusive education. Implications for the use of ISIS toward encouraging inclusive practices and enhancing a culture of inclusion are discussed. (Contains 4 notes, 9 tables and 2 figures.)