The theory of Gauss sums is
developed for integral quadratic forms over a local field of characteristic 2, and Gauss
sums are used to characterize these forms. For a character χ and an integral lattice
L, the Gauss sum χ(L) is either zero, a nonnegative power of two, or the
negative of a positive power of two. Gauss sums alone characterize the integral
equivalence classes for modular lattices. For arbitrary lattices, other invariants are
required.