  We introduce the fortran-library COLLIER for the numerical evaluation of
one-loop scalar and tensor integrals in perturbative relativistic quantum field
theories. Important features are the implementation of dedicated methods to
achieve numerical stability for 3- and 4-point tensor integrals, the support of
complex masses for internal particles, and the possibility to choose between
dimensional and mass regularization for infrared singularities. COLLIER
supports one-loop N-point functions up to currently N=6 and has been tested in
various NLO QCD and EW calculations.
