Polarized compton scattering from the proton

New precision measurements of cross sections and polarization asymmetries in thr p(<(gamma)over bar>,gamma p) reaction at 90 degrees c.m. are presented for incident energies between 213 and 333 MeV. A long-standing problem with earlier experiments that appeared to violate unitarity at the peak of the Delta is resolved. Data are compared to theories based on baryon resonance structure and to dispersion relations. Recent calculations using the proton polarizabilities are closest to the data, although inconsistencies are observed near the Delta resonance.