The purpose of this study was to investigate middle school general education mathematics teachers' beliefs and knowledge of inclusive instruction and to assess whether or not teachers' classroom practices reflect their beliefs and knowledge. Administrative support and higher education teacher preparation programs were also examined. Data were collected through survey methods, as well as through interviews and observations. The Survey on Teaching Mathematics to Students With Learning Disabilities in Middle School (DeSimone & Parmar, 2004), a three-part questionnaire specifically designed for this study, was piloted, and Cronbach's alpha coefficients were calculated followed by an item analysis. The final questionnaire was completed by 223 sixth, seventh and eighth-grade general education mathematics inclusion teachers from 19 different states. In-depth interviews and classroom observations were conducted with seven participants. Frequency analyses were performed on survey data, while the constant comparative method was used to analyze all interview and observation data. The findings revealed five central themes: (1) teacher collaboration was the most beneficial and available resource to general educators teaching mathematics inclusion; (2) general education mathematics teachers are not fully aware of their included students' level of attention or skilled at assessing their included students' comprehension of mathematics lessons; (3) inconsistency between general educators' beliefs and knowledge of instructional needs and/or required modifications for students with learning disabilities; (4) teacher education programs for mathematics general educators do not address teaching inclusion; and (5) administrators are not providing effective professional development and adequate preparation time for general educators teaching mathematics inclusion. Implications and recommendations for teacher education programs and middle school administrators, as well as suggestion studies, are provided. The following are appended: (1) Survey on Teaching Mathematics to Students With Learning Disabilities in Middle School; (2) Interview Questions; and (3) Phone Interviews. (Contains 6 tables.)