Prior to federal law PL-94-142, children with disabilities typically were excluded from regular, mainstream classes. This law emphasized the least restrictive environment since research had shown that all children benefited from inclusive learning environments. In the late 1990s, New Jersey was cited as having too high a proportion of children with disabilities in segregated placements. New Jersey received a State Improvement Grant (SIG) to increase the number of students with disabilities in regular education classes. This dissertation was designed to evaluate one aspect of local school districts' program initiatives to achieve this end: teachers' attitudes and perceptions regarding inclusion. Teachers are responsible for the daily implementation of inclusion practices. Their attitudes, perceptions, and beliefs are crucial for the success of inclusion. Although findings from previous research have indicated that teachers favor inclusion, their willingness to implement inclusive practices depends on the availability of supports and resources, as well as the attitudes of school personnel. A total of 856 general education, special education, and special area teachers from seven districts in New Jersey were surveyed regarding: (a) their attitudes and beliefs about inclusion; (b) their perceived administrative support; (c) their perceived ease in meeting the needs of students with disabilities in their classroom; and (d) the factors that have helped or hindered their ability to include students with disabilities in their classroom. Quantitative (Pearson product-moment correlation, multiple regression, independent samples t test) and qualitative (content analysis) methods were used to analyze the survey data. Special education teachers had more positive attitudes toward inclusion than did general education teachers. Relationships between teachers' attitudes and perceptions, and administrative support were found for general education teachers but not for special education teachers. Years of experience working with students with disabilities did not influence these relationships. Teachers identified training, positive attitudes, and support from colleagues, administrators, and other school personnel as factors facilitating inclusive practices. Barriers to implementation included large class size, insufficient planning time, lack of support from colleagues and school administrators, student behavior and ability, and teachers' negative attitudes. Implications for practice are discussed for administrators and school psychologists.