The study is a component of a larger investigation that focused on exemplary practice in science and mathematics education. This case study involved an investigation of two chemistry teachers in high schools in Perth, Western Australia. The study utilized an interpretive methodology in which the questions emerged from intensive observations of chemistry lessons in classes taught by the two teachers. The principal finding was that the two teachers focused on teaching for understanding. One teacher tended to emphasize whole-class activities while the other utilized more small-group and individualized activities. The teachers were successful in their goal of teaching for understanding because they were effective classroom managers and they had strong science content knowledge that enabled them to focus on instructional strategies that facilitated student understanding. They asked appropriate questions, responded to student questions, and used effective cognitive monitoring strategies. The teachers were able to teach effectively because they had adequate content knowledge and pedagogical content knowledge.