If a current pulse with a magnitude several times higher than the steady state optimum current is applied to a thermoelectric cooler, an instantaneously lower temperature than that reachable at the steady state can be obtained. Most previous studies of this transient cooling effect focus on the minimum temperature achievable for free standing thermoelectric (TE) elements. In this work, we systematically study the transient response of thermoelectric coolers with and without mass loads through examination of both the minimum temperature reached and the time constants involved in the cooling and the recovering stages. For integrated thermoelectric cooler-passive mass load systems, two distinguishable cooling regimes, uniform cooling and interfacial cooling, are identified, and the criterion for utilization of the transient cooling effect is established based on the time constants. Although the results of this work are generally applicable, the discussions are geared towards cooling of microdevices that are of current interests. (C) 2004 Elsevier Ltd. All rights reserved.