Nuclear power plants are currently operating throughout the world and are supplying more than one-sixth of the world's electricity. In spite of recent events in Japan, given the current rate of growth in electricity demand and the ever growing concerns for the environment, nuclear power remains a key technology that can help satisfy the need for electricity and other energy products if it can demonstrate (a) enhanced system reliability and safety, (b) minimal environmental impact via sustainable system designs, and (c) competitive economics. Since 2000, the United States in collaboration with the international community has begun research on the next generation of nuclear energy systems that can be made available to the market over the next couple of decades and may offer significant advances toward these challenging goals. For near-term deployment, advanced water-cooled thermal reactors are being ordered or are under construction. Beyond this next decade, there are future nuclear power systems [so-called Generation IV (Gen IV)] that require advances in materials, reactor physics, and heat transfer to realize their potential. In particular, the use of supercritical fluids in Gen IV nuclear systems has gained prominence. The focus of this paper is to summarize some of the key supercritical heat transfer topics that we are addressing to assure appropriate reliable design and operation of these advanced nuclear systems.