Theory of the Hadronic Light-by-Light Contribution to Muon g-2

I report on the theory, recent calculations and present status of the hadronic light-by-light contribution to muon g-2. In particular, I report on work done together with Eduardo de Rafael and Arkady Vainshtein where we get a^{HLbL} = (10.5 ± 2.6) x 10^{-10} as our present result for this quantity.