When student teachers experience difficulty during lesson implementation, seasoned cooperating teachers choose among 6 alternative strategies by which to assist. Collectively called cooperating teacher I'S, the strategies are as follows: ignore, intervene, interject, interact, interrupt, and intercept. Appropriate use of these strategies can be taught directly or made more explicit to cooperating teachers as a means to facilitate quick resolution of problems; maintenance of student teacher confidence, self-esteem, and classroom authority; cooperating teacher confidence in the mentor role; and active or passive choices as they may be appropriate to specific circumstances. Included is a brief summary of research about cooperating teachers and their feedback practices, a description of behaviors that generally prove to be ineffective in response to these situations, detailed descriptions of the 6 cooperating teacher 1's that appear to be effective, and a discussion of general observations and implications.Consider for a moment this common scenario: The student teacher is delivering a lesson carefully developed in collaboration with her cooperating teacher (CT).' The CT believes that extensive counsel provided during lesson development will ensure the student teacher's success, and current student teacher behaviors suggest confidence about an ability to implement the lesson exactly as it was planned. Then, suddenly, things begin to go awry. An unexpected student question, an incorrect statement by the student teacher, a misstep in the lesson sequence, escalating student confusion, malfunctioning equipment, disruptive student behaviors, or any number of unanticipated incidents befall, and the lesson begins to disintegrate at alarming speed. Within seconds, the CT faces a critical decision point: Is intervention appropriate at this time? If so, what form should that intervention take?In teaching, occurrences of this type are called critical incidents (Tripp, 1993) for good reason: If ignored or poorly handled by the student or CT, actual lesson outcomes nearly always veer away significantly from expected outcomes-sometimes with dangerous consequences. Additionally, student teachers may lose face in front of the very individuals they work so diligently to impress. The ideal, of course, is to avoid critical incidents of this type at all cost; the reality is that student teachers face such incidents many times during their culminating field experience. It is na'ive to expect otherwise because, developmentally speaking, learning to teach is akin to learning any other skill: It takes practice; there 62 DONNA M. POST are challenges to overcome; and mistakes are part of the learning process. Rather than expect student teachers to avoid critical teaching incidents, logic directs C T s and university supervisors toward research findings that explain how best to proceed when such incidents occur. Yet, little is written about typical CT behaviors during student teachers' critical incidents, how effectively CT behaviors resolve th...