Point defects have been created in GaN by various types of irradiation: electrons (1 and 2.5 Mev, and the spectrum from Sr-90): protons (0.15 MeV, 2 MeV, and 24 GeV); He ions (5.4 MeV)-, gamma -rays (Co-60); and sputtering and c-beam deposition of metals. They have been studied by temperature-dependent Hall-effect measurements (T-Hall), deep-level transient spectroscopy (DLTS), optically detected magnetic resonance (ODMR), positron annihilation spectroscopy (PAS), and photoluminescence (PL). Confirmed defect energies, and firm or tentative defect assignments, are as follows: T-Hall (donor at 0.06 eV, V-N); DLTS (electron trap at 0.18 eV (thermal 0.06 eV), V-N, electron trap at 0.9 eV, N-1 or Ga-1-X); ODMR (Ga-1 and Ga-1-X): PAS (V-Ga): PL (0.85 eV band with 0.88 eV zero-phonon line, O-N or O-N-Ga-1; 0.93 eV band; 3.37 eV line; 3.39 eV line). Many of these defect signatures have also been observed in as-grown GaN. Dislocations, of the threading-edge type, are found to be acceptor-like in n-type GaN.