Six energy systems, if successfully researched and developed, could offer large blocks of energy for the balance of the 20th century. These are: nuclear breeders, direct burning of coal in compliance with EPA regulations, synthetic high-Btu gas, low-Btu gas from coal and residual oil, synthetic liquid fuel, and waste for fuel. This article, based on a report of the ASME Task Force on Energy Conversion Research, attempts to identify the weaknesses in known technology for these systems and to indicate what R&D steps must be taken if these ar to succeed in their mission. For fast breeder reactor systems the Task Force recommends that the following steps be taken: Development and earliest possible demonstration of commercial-scale nuclear fast breeder technology applied to electric power generation. Continued development of liquid metal fast breeder reactors (LMFBR's) with expedition, inclusive of a reciprocal sharing of technology on an international basis. Expanded development programs on gas cooled fast breeder reactors (GCFBR's) to assure an option and continued evaluation of molten-salt breeder reactors (MSBR'S) and other breeder concepts having reasonable potential. Refs.