The ways in which principals have influenced or been influenced by four Teacher Corps projects are described and explained in case studies based on field interviews, observations, and a review of the documents produced in the course of the projects. The studies also provide the background both for an analysis of factors affecting the role of the principal and for the compilation of a user's manual for administrators and project staff. The studies were conducted in the second year of a five-year project lifespan. They report the observations of two-person teams who observed their assigned schools for a total of five days during two site visits. Within all four projects, the teams observed changes taking place in the organization, substantive direction, and distribution of authority. (Author/WD)