This study compares the Questionnaire on Teacher Interaction (QTI) constructed by Wubbels, et al., for six countries including The Netherlands, United States, Australia, Slovakia, Singapore, and Brunei. The Model for Interpersonal Teacher Behavior (MITB) as a "circumplex" model with specific properties is discussed and an overview of methods to analyze these properties is given. Earlier research on the validity and reliability of the QTI is discussed in terms of these methods. Finally, outcomes of analyses of the validity and reliability of the QTI using data from the six countries is presented. (KHR)