A simple and effective method for the extraction of interface trap distribution in ultrathin metal– oxide–semiconductor (MOS) structures is presented. By a critical analysis of bipolar-pulse-induced currents through MOS capacitors, a technique is developed to determine the energy distribution of the interface traps without requiring the knowledge of surface potential and doping profile in the semiconductor. The proposed technique can be efficiently used to probe electrical stress, hot-carrier, and radiation-induced interfacial degradations in ultrathin MOS structures.