Deep-level transient spectroscopy (DLTS) was used in this work to reveal information about deep defect levels in CuInS2 based solar cells. A strong variation of the defect spectrum from sample to sample was found. A minority carrier trap at 0.25 eV and a majority carrier trap at 0.35 eV were identified as bulk traps by variation of pulse height. Two majority carrier traps at 0.24 and 0.8 eV were confirmed as interface traps.