  We discuss the two-loop integrals necessary for evaluating massless 2 to 2
scattering amplitudes. As a test process, we consider the leading colour
two-loop contribution to qqbar to q'qbar'. We show that for physical scattering
processes the two Smirnov-Veretin planar box graphs I1 and I2 are accompanied
by factors of 1/(D-4) thereby necessitating a knowledge of both I1 and I2 to
O(epsilon). Using an alternative basis I1 and the irreducible numerator
integral I3, the factors of 1/(D-4) disappear.
