We present an overview of implementation and application of low rate Deep-Level Transient Spectroscopy (LR-DLTS). In conventional DLTS the sensitivity of the capacitance meter must be chosen so low that the whole capacitance drift range between lowest and highest temperature can be measured. In LR-DLTS the bridge is automatically balanced (capacitance and conductivity) after each measured transient. Thus, the highest available sensitivity still avoiding an overload can be used. With LR-DLTS it is now possible to extend the rate windows to the mHz range while preserving highest possible sensitivity. This allows the detection of energetically close levels and levels with large thermal activation energy. Also low emission rates in optical DLTS can be detected this way. (C) 2013 Elsevier Ltd. All rights reserved.