By the turn of the century, the societal expectation that teachers should be better educated than the general population will require that teachers have a master's degree. Data showing a modest relationship between the percentage of teachers within a district holding the master's degree and student achievement are presented. The probable effect of state policy requiring teachers to obtain a master's degree on this relationship is discussed. It is recommended that states offer adequate and equitable salary incentives to teachers with a master's degree and that they institute policies that allow beginning teachers with a bachelor's degree to receive provisional certification but require a master's degree after a specified number of years for permanent certification. Knapp, McNergney, Herbert, and York (1990) argued that their cost/benefit analysis does not warrant implementation of a state policy requiring a master's degree for career teachers. In this article, I contend that the master's degree will be a requirement for teaching by the end of this decade and that cost/benefit calculations will have little bearing on whether states implement such a policy, although cost/benefits may affect its timing. The primary determinant of this policy is the societal expectation that teachers should be better educated than the general population.Professionalism requires that teachers have demonstrable efficacy in teaching, that they receive equitable incentives and remuneration, and that they be empowered to make decisions about their work. Baccalaureate preparation of teachers fails to provide sufficient time for the adequate development of professionalism. Master's-level education is necessary, if teachers are to achieve the professionalism society requires. The principal issue for teacher education in the 1990s is whether schools, colleges, and departments of education can respond to this challenge. I offer a rationale for the requirement of the master's degree for teachers and suggestions for how such a policy could be implemented.