This paper describes a method of reflective practice called "critical incident" which was used to examine teacher trainees' educational assumptions. A qualitative case study of one fifth-year teaching intern (Amy) at the University of Tennessee represents the experience of seven other master's level students already practicing within the elementary classroom. The research investigated how reflective practice can serve the classroom teacher. Three major assumptions about reflective practice were that: (1) beliefs and values, learned early in life as cues and symbols from parents, will affect actions of beginning teachers; (2) teachers who practice reflection about their teaching decisions will become lifelong learners; and (3) the combined knowledge of teaching professionals as they collaborate will be greater than the sum of the parts of individual knowledge. The theoretical basis for the study was transformation theory, which implies that one's personal assumptions based on beliefs and values will change during a reflective process about actions taken during a critical incident. Study participants wrote retrospective educational autobiographies describing their experience of school, then wrote about a "critical incident" from daily practice in their own teaching experience. Finally, in classroom discussion, the graduate teacher education students searched for assumptions as a result of the learning that took place during the process. Findings led to the recommendation that reflective practice be used as an action-oriented means of understanding one's underlying assumptions about teaching in the classroom. (ND)