This chapter reviews the published and unpublished research about parent and teacher ratings of young children's mastery motivation. It introduces a useful questionnaire to readers and demonstrates its utility, especially what it can add to other research approaches to mastery motivation. The chapter divides into the following sections: development of the questionnaires; their reliability; their validity; correlates of mastery motivation; and conclusions and recommendations. In the Manitoba pre-school study mothers rated their child higher than did teachers on three scales and fathers rated higher than teachers on four scales. It was not surprising that mothers and fathers rated their children somewhat higher than teachers, but it was surprising that the scales on which such teacher-parent differences occurred were generally not the same for the US and Canadian groups. From the pattern of parent and teacher responses to the Dimensions of Mastery Questionnaire (DMQ), it founds support for an expressive component of mastery motivation mastery pleasure.