This study explored teachers' pedagogical strategies for using multimedia simulation to structure and support secondary science teaching. Expertise was investigated across a range of classroom settings to analyse how specialist knowledge is situated within and adapted to the teaching and learning context. Analysis of data arising from 10 lesson observations and post-lesson interviews with five teachers and their pupils highlighted significant variation in pedagogical approaches shaping simulation use in three topic areas. Two contrasting case studies involving a "terminal velocity" simulation exemplify this: one was characterized by some "dialogic" whole class interaction and collaborative testing of pupils' own ideas; the other by a more typical, more authoritative, discourse with pupil pairs. Over-structuring of tasks and curricular constraints meant that the rhetoric in the literature and teachers' aspirations concerning pupil experimentation balanced with structured tasks were not borne out. Implications for mode of use and the design of technology-integrated activity are discussed. (Contains 2 tables and 9 notes.)