This article presents a motivational conceptualization of engagement and disaffection: First, it emphasizes children's constructive, focused, enthusiastic participation in the activities of classroom learning; second, it distinguishes engagement from disaffection, as well as behavioral features from emotional features. Psychometric properties of scores from teacher and student reports of behavioral engagement, emotional engagement, behavioral disaffection, and emotional disaffection were examined using data from 1,018 third through sixth graders. Structural analyses of the four indicators confirm that a multidimensional structure fits the data better than do bipolar or unidimensional models. Validity of scores is supported by findings that teacher reports are correlated with student reports, with "in vivo" observations in the classroom, and with markers of self-system and social contextual processes. As such, these measures capture important features of engagement and disaffection in the classroom, and any comprehensive assessment should include markers of each. Additional dimensions are identified, pointing the way to future research. (Contains 2 figures and 5 tables.)