Recent trends for next generation microprocessors clearly point to significant increase in power consumption, heat density, and to corresponding challenges in thermal management. In desktop systems, the trend is to minimize system enclosure size while maximizing performance, which in turn leads to high power densities. The thermal management technologies used today consist of advanced heat sink designs and heat pipe designs with forced air cooling. However, these techniques are approaching fundamental limits for high heat flux, and there is a growing need for development of more efficient and scalable cooling systems. To this end, a new closed loop liquid cooling system has been developed to handle heat fluxes greater than 500 W/sq cm. The cooling system comprises a micro channel heat exchanger for high heat flux removal, an electro-kinetic pump for delivering fluid with required flow rate and pressure, and a counterflow heat rejector to dissipate heat to the ambient. The thermal performance of such a system was analyzed with ICEPAK. Experimental work was carried out to validate the modeling results and evaluate performance for a high end computer system cooling application.