  We study non-linear corrections to the low-energy description of the (2,0)
theory. We argue for the existence of a topological correction term similar to
the C3 wedge X8(R) in M-theory. This term can be traced to a classical effect
in supergravity and to a one-loop diagram of the effective 4+1D Super
Yang-Mills. We study other terms which are related to it by supersymmetry and
discuss the requirements on the subleading correction terms from
M(atrix)-theory. We also speculate on a possible fundamental formulation of the
theory.
