Majority-carrier traps are characterised for n- and p-type GaAs. Bulk and vapour-phase-epitaxial n GaAs show the same electron-trap centre (0.83 eV). No electron traps were detected in liquid-phase epitaxial n GaAs, but three hole trap centres (0.64, 0.44 and ∼ 0.6 eV) were found in p GaAs. The capture cross-section and density of these centres have also been determined.