ABSTRACT. Inter-rater reliability of the Motivation Assessment Scale (MAS) was assessed for independent ratings of 12 adolescents and adults with severe/profound mental handicap. Correlations of item and subscale scores across raters were low. The internal consistency of subscales and total scores of the MAS was high. It is suggested that future research using the MAS should include an analysis of the reliability of this measure and features of the raters and subjects which might limit the robustness of the MASJ