Forty-four student teachers' existing understanding of Information and Communications Technology (ICT) and the way it changes as they learn to teach is examined. The cohort were taking a postgraduate certificate in education course at the University of Cambridge UK in 2000-2001. Data from assignments, questionnaires and interviews were analysed. The students had a variety of views about teaching using ICT. Their understanding of ICT became more sophisticated over the year in three stages, which involved processes of personalisation, growth of pedagogical sensitivity and the development of contingent thinking. Students valued reflective assignments, university-based tuition and experience of teaching using ICT as ways of developing their thinking and practice. Implications of the findings for those involved in teacher education are suggested.