This qualitative study explored teachers' perceptions of the inclusive education of students with autism spectrum disorder (ASD) at the post-primary level, specifically those with Asperger syndrome. Semi-structured interviews were conducted with eight mainstream teachers in the Republic of Ireland. One of the main findings of the study was that the teachers' implicit model of inclusion was more consistent with integration than with inclusive education. Although systemic barriers to inclusive education were identified, the teachers' focus tended to be on managing within the system rather than on bringing about systemic change. Mainstream post-primary education was endorsed by teachers for their students with ASD, despite perceiving that these students were unhappy and socially excluded. The teachers were confident in teaching students with ASD, primarily as a result of their experience. The implications of the study for teacher educators and future researchers are discussed.