The present research investigated the changing processes of perceiving and judging groups of different ethnic backgrounds. Of particular interest were the testing of the validity of Pettigrew's Intergroup Contact Model and identification of changes in the perception of Germans over time, the identification of the variables mediating the changing process, and the identification of a moderating effect of extroversion on the stereotypes. The study had a longitudinal design with the first measurement done before intercultural contact followed by the second during the stay in the host country and the third after the contact was completed. A sample comprising 120 Colombian exchange students formed the focus of the study. Results provide evidence that intergroup contact can lead to positive effects on outgroup bias, that changing behavior, ingroup reappraisal, and generating affective ties did not play a role as mediating variables, and that extroversion did not have a moderating effect on the attitude changing process.