Background: The four-phase model of interest development is a widely accepted theoretical perspective on the development of long-term interest. Our future teachers will be faced with the task of developing their students' long-term interest in science. Yet it is not known whether they have workable ideas for how to achieve this. Purpose: The purpose of this study was to identify preservice teachers' ideas about how to increase students' long-term interest in science. Sample: The participants were 235 preservice primary teachers and 33 preservice secondary science teachers. Design and Methods: Data collection was by questionnaire, interview and classroom observations. Results: It was found that participants in both primary and secondary groups had very similar ideas about how to develop pupils' long-term interest in science. These ideas mainly involved the use of hands-on activities, making science relevant, and using student-centred strategies or electronic media to make lessons fun and to enhance engagement. These can be interpreted as representing sources of situational interest (i.e. short-term interest arousal). These ideas broadly parallel the current theory on interest development, such that long-term individual interest is thought to develop from repeated experiences of short-term, situational interest. Conclusion: The participants' ideas in this study were intuitive, because they were not derived from an understanding of theory, but rather from their personal experiences of interest arousal at university, school and practicum. Nevertheless, their ideas were workable for a practitioner, because they broadly paralleled current theory on interest development.