This research goes with a new tendency in the field of educational psychology--the study not only of students' motivation but also of teachers' motivation. However, the studies of teacher motivation had been only to acknowledge the factors to motivate teachers, without the analysis of motivation as a process that contains several cognitive variables. This research analyzed teacher's motivation to motivate students using the Ajzen's Theory of Planned Behavior (1985). This is one of the most thorough theories of human motivation because it integrates variables from several other contemporary theories. By this theory, behavior is predicted, taking into account the personal attitudes, intentions, perceived control, and subjective norm concerning this behavior. These variables are assessed by a 7-point likert type scale. Factorial analysis resulted in four factors, each one corresponding to the group of items that assess one of the variables. The results obtained with a sample of teachers and preservice teachers (n=143) showed that, in general, the relationships between these motivational variables are as expected by the theory, predicting behavioral expectations in what concerns personal implication in classroom tasks. (Contains 20 references.) (Author/ND)