Although students' invented strategies typically prove to be effective in the improvement of students' mathematical understanding, little is known about how preservice teachers interpret and respond to student-invented strategies on whole number multiplication. This study investigated the nature of 25 preservice teachers' interpretations of and responses to students' correct and incorrect strategies for whole number multiplication. Results suggest that the mathematical depth of their responses and their consideration of student thinking differed based on the correctness of the student work. Implications for teacher educators and future researchers are discussed in accordance with the findings of the study. [For the complete proceedings, see ED584443.]