This paper presents the psychometric properties of a questionnaire measure that updates and extends Larrivee and Cook's (1979) Opinions Relative to Mainstreaming Scale in terms of structure, terminology, and language. The revised scale was tested using a sample of 106 teachers based in inclusive mainstream schools. Using Principal Component Analysis, a four-factor structure was found for the "attitudes toward inclusion" section of the revised scale: (a) problems of inclusion of special educational needs (SEN) children in mainstream classes; (b) social benefits for all of the inclusion of SEN pupils in mainstream classes; (c) implications of inclusion for teaching practice; and (d) implications for addressing the needs of children with SEN. Moderate to good reliability was found for these components (Cronbach's a: 0.76-0.86). In conclusion, the updated and revised Teachers' Attitude to Inclusion Scale (TAIS) shows promise of being a reliable and valid measure for both research and applied purposes.