This study investigated Canadian high school teachers' attitudes toward the inclusion of students with special education needs in the general classroom environment. Teachers' cognitive, affective, and behavioural attitudes toward inclusion were examined. Data were collected by using a 7-point Likert scale survey called the Inclusion Scale for High School Teachers created by Dr. Catherine Ernst (2006). The survey, which included a demographic questionnaire as well as cognitive, affective, and behavioural attitude statements regarding inclusive practices, was conducted with a population of 150 high school teachers from a single urban school division in a large city in central Canada. Participants' demographic information was analyzed using descriptive statistics. The Somers' Delta ("Somers" D) statistic was used to determine the strength and relatedness of the independent variables of teacher demographics and school environmental variables to the dependent variable of teacher attitude. Findings showed that high school teachers' attitudes toward inclusion were more positive than negative. The teachers' behavioural attitudes toward inclusion were most positive, while their affective attitudes toward inclusion were least positive. The demographic variables with the greatest influence on teacher attitudes toward inclusion were (a) experience as lead teacher in an inclusive setting, (b) access to human resources and supports, and (c) professional development and training related to inclusion. This study is of particular importance because it is the first study to focus specifically on Canadian high school teachers' attitudes toward inclusion.