Experimental status of the GDH sum rule

An experimental program to investigate the Gerasimov-Drell-Hearn (GDH) sum rule on protons and neutrons has been carried out by the GDH collaboration at MAMI (Mainz) and ELSA (Bonn), using circularly polarized photons and the Bonn-Bochum longitudinally polarized frozen-spin target together with two different detector setups. For the proton, results in the photon energy range 200 - 2985 MeV are published. Preliminary data from JLab extend the energy range to 5.2 GeV. For E-gamma < 800 MeV the helicity structure of partial reaction channels has been studied in detail at MAML Data from polarized deuterons have also been taken at photon energies 200 - 800 MeV (MAMI) and 815 - 1825 MeV (ELSA). Preliminary results and future perspectives are presented and discussed.