  We study massless one-loop box integrals by treating the number of space-time
dimensions D as a negative integer. We consider integrals with up to three
kinematic scales (s, t and either zero or one off-shell legs) and with
arbitrary powers of propagators. For box integrals with q kinematic scales
(where q=2 or 3) we immediately obtain a representation of the graph in terms
of a finite sum of generalised hypergeometric functions with q-1 variables,
valid for general D. Because the power each propagator is raised to is treated
as a parameter, these general expressions are useful in evaluating certain
types of two-loop box integrals which are one-loop insertions to one-loop box
graphs. We present general expressions for this particular class of two-loop
graphs with one off-shell leg, and give explicit representations in terms of
polylogarithms in the on-shell case.
