  We study the effective action of quantum mechanical SU(N) Yang-Mills theories
with sixteen supersymmetries and N>2. We show that supersymmetry requires that
the eight fermion terms in the supersymmetric completion of the $v^4$ terms be
one-loop exact. We also show that the twelve fermion terms in the
supersymmetric completion of the $v^6$ terms are two-loop exact for N=3. For
N>3, this no longer seems to be true; we are able to find non-renormalization
theorems for only certain twelve fermion structures. We call these structures
`generalized F-terms.' We argue that as the rank of the gauge group is
increased, there can be more generalized F-terms at higher orders in the
derivative expansion.
