Exclusive two-photon reactions such as Compton scattering at large angles,
deeply virtual Compton scattering, and hadron production in photon-photon
collisions provide important tests of QCD at the amplitude level, particularly
as measures of hadron distribution amplitudes and skewed parton distributions.Comment: Invited talk presented at Photon 2000, Ambleside, England, August
26-31, 200
