This paper describes a study done to better understand teacher leadership as it is currently practiced in public schools. The study was an exploratory one, consisting of three case studies of teachers who hold leadership positions within their schools. Each of the teacher leaders played a distinctly different kind of leadership role; worked at a different level in the K-12 system; worked in a different kind of educational setting from rural to suburban, and existed in a uniquely different context. This paper briefly reviews the framing questions of the study (e.g., What is the nature of the lead teacher's work? What are the constraints and supports of their positions? How are teacher leaders selected and evaluated? Next, a summary is presented of the literature on teacher leadership, following which the case study methodology is discussed and the data sources described. A "snapshot" description of each of the cases studied is then provided, the findings are reviewed, and the implications for both rhetoric and real practice are discussed. In general, it was found that these teacher leaders were constrained by their lack of time, by the original conceptions of their roles, and by the egalitarian ethic in teaching. In all cases, administrative support was crucial. Implications for further research are briefly discussed. (JD)