An examination of the ways in which teachers gain and use knowledge about their work is presented through a case study using retrospective interviews with a high school English teacher in Canada. The teacher's "practical knowledge" was explored in a series of open-ended discussions, dealing with the teacher's involvement in the development of an experimental course and with various issues, including attitudes toward teaching and learning, conception of subject matter in two areas (English and reading), and values, commitments, and career plans. These discussions were supplemented by two periods of observation in the classroom and in a reading center. The series of discussions and observation reports provide data about: (1) practical knowledge and teachers' experiential learning; (2) content of practical knowledge--self-knowledge, subject matter knowledge, and curriculum and instruction knowledge; and (3) orientation and structure of practical knowledge, cognitive style, and reflections on research activity in this area. (JD)