Schools across the United States are creating teacher teams in ever-greater numbers. "Teaming" refers to assembling a group of teachers from different disciplines and/or grade levels who work together as a "core group" responsible for teaching a subset of the school's population. This brief examines some of the potential conflicts between teacher teaming and the development of schoolwide professional community. Drawing on the actual experiences of teachers and administrators in schools, the brief illustrates some of the more common dilemmas faced by schools with a strong commitment to teams. The first section summarizes what has been learned about professional community and its importance to schools. The following sections examine four middle schools that participated in research on school restructuring. In all four schools, teachers expressed enthusiastic support for teaching, but when researchers from the Center on Organization and Restructuring of Schools began looking at teacher teams in hopes of gaining insight into how teachers think about their work, another important pattern emerged. Teachers reported that teams tended to undermine the ability of the whole faculty to deal with the business of the whole school. The following specific dilemmas sidetracked teachers' attention to schoolwide issues and the development of a schoolwide professional community: time conflicts between team or whole-school issues; increased involvement with their group of students; limited time for peer observation; competition between teams; and the tendency within teams to compromise rather than risk serious disagreement, possibly leading to important issues being watered down. It is hoped that by presenting examples of problems that other schools encounter, teachers, principals, and other educators will learn from their colleagues' experiences and use them as a guide in developing or assessing their own schools and programs. (LMI)