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In this paper, the results of an experimental study have been reported of a high heat flux cooling system for thermal management of high power electronics. The objective of this study is to investigate whether or not a practical design solution exists for easily achieving 1000 W/cm2 cooling of microwave electronics. A laboratory test module was designed, built, and tested to verify its performance. The experimental system employed sub-cooled as well as saturated forced convection boiling heat transfer in a parallel microchannel heat sink. The working fluids tested were water and a selection of ceramic-based nanoparticle suspensions (nanofluids). The system was observed to dissipate heat fluxes in excess of 275 W/cm2 of the substrate, while maintaining the substrate at or below 125°C. For optimized fin geometry, the current conditions would result in greater than 500 W/cm2. While the use of nanofluids was intended for boiling enhancement with reduced flow maldistribution in the microchannels, we discerned limited improvement in the overall heat transfer rate. Future studies are planned for further investigation of nucleate boiling of nanoparticles.