The main reasons for conducting research and development (R&D) on an advanced pressurized water reactor (APWR) with a high conversion ratio include an awareness of the limited availability of natural nuclear fuels, the low degree of utilization of this resource in present light water reactors (L WRs), and the necessary high capital investments in breeder reactor systems with high fuel utilization. Consequently, these R&D efforts, on the one hand, must greatly increase the utilization of uranium compared to the level achieved in L WR technology and, on the other hand, must reduce the capital investment compared to what is required in breeder reactor technology. If these criteria can be met economically, a future role would be indicated for APWRs as an interim technology during the transition from LWRs to breeder reactors and as a supplement to the latter line in a breeder/APWR symbiosis. It appears that an APWR will use nuclear resources economically but will also create higher costs for an electric utility than current LWR technology.