The California Mentor Teacher Program, brought into being by California Senate Bill 813, is designed to retain and recognize excellent teachers and to improve the profession by enabling expert teachers to assist others. Four major issues to consider in developing mentor teacher programs are discussed. First is the importance of collaboration with appropriate groups in planning, including teachers, governing boards, and administrators. Second, program design should reflect local needs and priorities. Design possibilities include (1) a master teacher to provide staff development; (2) a mentor as a trainer of new teachers; (3) a mentor teacher as a "fellow" in a teacher training academy; or (4) a mentor teacher as a curriculum developer. Third, the criteria for the selection of mentor teachers in the California Mentor Teacher Program are set by the California Education Code, but they allow considerable flexibility to local districts. The Code stipulates only that mentor teachers should have credentials and permanent status, substantial classroom experience, and demonstrated teaching ability. Finally, mentor teachers in their new role may require training and support from site administrators and teachers. Partial state funding has been provided for stipends to mentors. (TE)