Hyman Bass's mathematical research publications cover broad areas of algebra with connections to geometry, topology, and number theory. He is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. Bass was president of the American Mathematical Society and of the International Commission on Mathematics Instruction. He has been collaborating with Deborah Loewenberg Ball and her research group at the University of Michigan since 1997 on the mathematical knowledge and resources entailed in the teaching of mathematics at the elementary level. Bass is interested in algebra/algebraic geometry and mathematics education. Chief fields of his research interest are: in mathematics – algebraic K-theory, number theory, group theory (geometric methods), and algebraic geometry; in mathematics education – subject matter knowledge entailed in teaching, practice-based research on teaching and learning, teacher education, reasoning and proof in school mathematics, and analysis of curriculum materials. His main research activities currently are in math education, focused largely on the mathematical knowledge demands of school teaching, how this can be measured, and the design of opportunities for teachers to gain such knowledge (in teacher education courses and in professional development). In mathematics he still is working on a project on flat families of reductive group actions on affine spaces, and also some arithmetic questions in combinatorial geometry.