  We perform a lattice QCD calculation of the hadronic light-by-light
scattering amplitude in a broad kinematical range. At forward kinematics, the
results are compared to a phenomenological analysis based on dispersive sum
rules for light-by-light scattering. The size of the pion pole contribution is
investigated for momenta of typical hadronic size. The presented numerical
methods can be used to compute the hadronic light-by-light contribution to the
anomalous magnetic moment of the muon. Our calculations are carried out in
two-flavor QCD with the pion mass in the range of 270 to 450MeV, and contain so
far only the diagrams with fully connected quark lines.
