In this research we examined and assessed the impact of implementation of a model using authentic investigative activities for teaching ratio and proportion in pre-service teacher education. The model was developed following pilot studies investigating the change in mathematical and pedagogical knowledge of pre- and inservice mathematics teachers due to experience in authentic proportional reasoning activities. The conclusion of the study is that application of the model, incorporating theory and practice leads to a dramatic positive change in the pre-service teachers' content and pedagogical knowledge. In addition, an improvement occurred in their attitudes and beliefs towards learning and teaching mathematics in general, and ratio & proportion in particular. (Contains 2 figures and 2 tables.) [For complete proceedings, see ED489538.]