  Two-loop corrections for the form factor in a massive Abelian theory are
evaluated, which result from the insertion of massless fermion or scalar loops
into the massive gauge boson propagator. The result is valid for arbitrary
energies and gauge boson mass. Power-suppressed terms vanish rapidly in the
high energy region where the result is well approximated by a polynomial of
third order in ln(s/M^2). The relative importance of subleading logarithms is
emphasised.
