  We discuss the determination of the infrared singularities of massive
one-loop 5-point functions with Mellin-Barnes (MB) representations. Massless
internal lines may lead to poles in the $\eps$ expansion of the Feynman
diagram, while unresolved massless final state particles give endpoint
singularities of the phase space integrals. MB integrals are an elegant tool
for their common treatment. An evaluation by taking residues leads to inverse
binomial sums.
