The Norwegian school system gives a high priority to information and communication technology (ICT), and its ICT density is high, with one laptop per student considered desirable and being nearly accomplished. This study seeks to find the reasons for aspects of Norwegian teachers' pedagogical behaviour and choices by focusing on their thoughts and practices in technology-rich classrooms and by analysing how they explain them. It aims to enhance our understanding of how teachers in leading-edge schools appreciate the possibilities of a technology-rich environment, using theories about teachers' technological pedagogical content knowledge as a framework. The informants in this study had worked as teachers in upper secondary schools for at least five years and were categorised as digitally competent. Interviews conducted early in the study showed them struggling to explain their ICT use because teaching is a complex activity and ICT can not be isolated from it. To increase the validity of the study it was therefore necessary to employ a more composite research method, collecting data from the researchers' and the schools' reports and from development work with ICT, interviews with teachers, videotaped lessons, videotaped discussions with teachers after lessons, and videotaped discussions involving teachers sharing their reflections with colleagues. The study shows that if teachers do not feel comfortable with changes, teaching practices stay the same. At the same time these teacher have developed, and have continued to develop, a digital pedagogical content knowledge which seems to be necessary in the digitised school of today. (Contains 2 figures and 4 tables.)