This paper considers the responses of 26 teachers to items exploring their pedagogical content knowledge (PCK) about the concept of average. The items explored teachers' knowledge of average, their planning of a unit on average, and their understanding of students as learners in devising remediation for two student responses to a problem. Results indicated a wide range of performance and a wide range of ability in realtion to a hierarchical statistical PCK scale. Suggestions are made about developing teachers' PCK. [This research was funded by ARC Linkage Grant No. LP0669109 in collaboration with the ABS, Key Curriculum Press, and the Baker Centre for School Mathematics, Adelaide.]