Cooperating teachers are believed to have a tremendous influence on new teachers' beliefs and practices, but few researchers have systematically studied the mechanism through which cooperating teachers exercise their influence. This study is concerned with pedagogical interaction that occurs between intact pairs of cooperating and student teachers. Specifically, we examined predictors of cooperating teachers' self-reported pedagogical interaction with their student teachers. Results indicate that the efficacy beliefs of cooperating teachers, and the extent to which they believed student teachers imitated their instruction, predicted how much guidance cooperating teachers reported providing. Implications for further research and for student teaching are discussed. (Contains 2 tables. Learning to Teach Questionnaire (LTQ) Items by Subscale is appended.)