Graduate teaching assistants are often left out of the science teacher education reform agenda, but these science educators are responsible for significant amounts of undergraduate instruction especially at large research universities. Within science departments specifically, a number of courses and laboratories are taught by graduate teaching assistants (GTAs). The role of GTAs in undergraduate science education, their pedagogical beliefs and instructional approaches are briefly discussed. An analysis of the structure, components, quality, and effectiveness of science GTA teacher preparation programs in the research literature is reviewed. Finally, goals for future science teacher education and sustained professional development of science GTAs are offered based on the results of the review. (Contains 1 table.)