  We give an update on the status of the hadronic light-by-light scattering
contribution to the muon g-2. We review recent work by various groups, list
some of the open problems and give an outlook on how to better control the
uncertainty of this contribution. This is necessary in order to fully profit
from planned future muon g-2 experiments to test the Standard Model. Despite
some recent developments, we think that the estimate a_{mu}^{HLbL} = (116 \pm
40) x 10^{-11} still gives a fair description of the current situation.
