 He is a professor at the University of Bielefeld.He is known for his work on norm varieties (a key part in the proof of the Bloch–Kato conjecture) and for the Rost invariant (a cohomological invariant with values in Galois cohomology of degree 3).Together with J.-P. Serre he is one of the cofounders of the theory of cohomological invariants of linear algebraic groups.