A direct measurement of the helicity dependence of the total inclusive photoabsorption cross section on the proton was carried out in the energy range from 200 up to 3000 MeV for the first time. The experiments were performed at the Mainz accelerator facility MAMI (200-800 MeV) and at the Bonn accelerator ELSA (800-3000 MeV). 4π detector systems, circularly polarized tagged photon beams and a newly developed polarized solid target were used. The data obtained provide new information for multipole analyses of pion photoproduction and give contributions to the Gerasimov-Drell-Hearn (GDH) sum rule.