The Learning in Science Project identified the learner as the key perspective for in-depth study into problems and difficulties in the teaching and learning of science at the 10- to 14-year-old level. Two complementary research foci were established to explore this viewpoint: (1) interviewing children using strategies designed to establish various meanings held for words used in science and to identify children's views of various phenomena and (2) observing typical science lessons in an attempt to better understand the nature of children's classroom experiences. This paper is particularly concerned with methodologies used to observe children at work in their science classrooms and to handle data collected from these observations. Strategies used include case studies of specific lessons (the single lesson portrayal) and classroom issues in typical science lessons. Unobtrusive observation was employed to record action, dialogue, and comments from students, teachers, and observers of four aspects of the single lesson (nature of lesson set, set task, and students' actions/thinkings). Observational mechanisms for classroom issues included developing a comprehensive strategy for obtaining/analyzing information on the activities/perceptions of a single observer and applying "grounded theory" strategies to the many lesson-records obtained. (A framework for analyzing lesson-records and selected extracts from observations illustrating the research methodology are included in appendices.) (JN)