This paper attempts to discover and describe the salient common factors constituting four high school science teachers' role conceptions. In a year-long ethnographic study, two researchers worked as participant observers in various science classroom settings at an urban high school. Teachers in charge of these classrooms were interviewed on issues related to their classroom practices in general and role conceptions in particular. Assertions regarding teachers' role conceptions were made. Teachers see their role as primarily related to classroom happenings; they maintain a sense of groupness through planning and organizing learning activities. Teachers envision part of their role to be subject matter specialists and some of them try to attract high enrollments in science courses. The paper offers suggestions regarding possible factors contributing to high school science teachers' role conceptions such as: (1) their role models; (2) educational background; (3) socialization by peers; and (4) job protectionism. Implications of these teachers' practices and role conceptions are highlighted and specific implications for teacher education are discussed. (YP)