Deep energy levels of deformation-induced defects in n-type GaAs crystals are studied by means of isothermal capacitance transient spectroscopy (ICTS). Analysis of the transient curves shows that three kinds of electron traps, termed ED1a, ED1b, and ED2, and one kind of hole traps, termed HD1, are induced by deformation. Additional deformation-induced acceptors, termed X, might also be introduced near the valence band. The energy levels and capture cross sections of ED1a and ED1b are determined as Ec − 0.55 eV, 2.9 × 10−17 cm2 and Ec − 0.60 eV, 1.3 × 10−15 cm2, respectively, and those of ED2 as Ec − 0.41 eV and 4.3 × 10−16 cm2. HD1 is observed with filling pulses longer than 1 ms. The energy level and hole capture cross section of HD1 are determined to be Ev + 0.66 eV and 8.4 × 10−13 cm2, respectively. HD1 is found to be less stable than ED1a and ED1b againstthermal annealing.