This report--based on an exploratory empirical study of state certification and licensure policies, 10 states' employment databases, a survey of teachers with interstate mobility experience, and focus groups of American Association for Employment in Education members and Troops-to-Teachers state directors--focuses on the certification and licensure aspect of the facilitators and barriers to teacher interstate mobility. It also includes an exploration of the unique mobility experiences of participants in the Troops-to-Teachers program. The analysis described in this report indicates that states have much common ground in their policies toward teacher licensure and reciprocity, yet differences remain. Motivated state directors of teacher education and certification must address these obstacles while maintaining high levels of quality. Continuing widespread teacher shortages in certain fields and the dim prospects that these shortages will disappear anytime soon provide a clear impetus for change. Based on the findings of this study, the need to build better infrastructure--including better data systems and communication channels--is clear. The challenges of the 21st century demand that the problems of interstate teacher mobility be addressed. Appended are: (1) Project Design; and (2) State Extant Teacher Data Tables. (Contains 2 tables, 3 figures and 1 footnote.)