Advances in miniaturization have led to the use of microchannels as heat sinks in industry. Studies have established that the thermal performance of a microchannel depends on its geometric parameters and flow conditions. This paper describes two approaches for determining the optimal geometric parameters of the microchannels in micro heat exchangers. One approach combines CFD analysis with an analytical method of calculating the optimal geometric parameters of micro heat exchangers. The second approach involves the usage of multi-objective genetic algorithms in combination with CFD. (c) 2005 Elsevier Ltd. All rights reserved.