The influences of configurations on the performance of microchannel heat exchangers were studied experimentally. The parameters associated with geometrical configuration consist of substrate thickness, cross-sectional area, and inlet/outlet locations. In order to evaluate the effects of these parameters, two categories of fluid flow conditions (varying the inlet temperature of hot side and varying the mass flow rate of cold side) were considered. In this study, the highest performance index (expressed as the ratio of the heat transfer rate to the pressure drop) of 21.67 W/kPa was achieved for the heat exchanger with the thinnest thickness; the highest heat flux of 18.7 W/cm 2 was achieved for the heat exchanger with the shallow channel; and the lowest pressure drop of 506 Pa was achieved for the heat exchanger with the I-type, as compared to those with the S-type.