This paper reports a study of the impact of an initial teacher education programme on the development of a conceptual change model of instruction in prospective biology teachers. Analysis of the performance in teaching practice indicates that the subjects achieved significant improvement in the various skills related to this instruction model. However, mastery of these skills was not evident, especially in the response to pupils' alternative conceptions, the presentation of chalkboard layout, the use of high order questions to probe understanding and facilitate concept development, and the conduct of interactive learning activities. This can be related to the subjects' lack of teaching experience and inadequate subject knowledge, the passive learning attitude of pupils, constraints in time and resources, and the non-supportive conditions in schools.[Copyright of International Journal of Science Education is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/09500690010016067]