  We present general prescriptions for the asymptotic expansion of massive
multi-loop Feynman integrals near threshold. As in the case of previously known
prescriptions for various limits of momenta and masses, the terms of the
threshold expansion are associated with subgraphs of a given graph and are
explicitly written through Taylor expansions of the corresponding integrands in
certain sets of parameters. They are manifestly homogeneous in the threshold
expansion parameter, so that the calculation of the given Feynman integral near
the threshold reduces to the calculation of integrals of a much simpler type.
The general method is illustrated by two-loop two-point and three-point
diagrams. We discuss the use of the threshold expansion for problems of
physical interest, such as the next-to-next-to-leading order heavy quark
production cross sections close to threshold and matching calculations and
power counting in non-relativistic effective theories.
