This paper reports on 12 in-depth case studies of trainee science teachers' use of the Internet in their science teaching from teacher training programmes in four UK universities. The findings reveal many opportunities and challenges trainee teachers face in using the Internet and these are examined in the light of the promotion of the use of ICT in general and the Internet in particular, both in the UK and on an international scale. The analysis draws out implications for science teacher education programmes and future practice. (Contains 2 tables and 1 note.)