Abstract-- Field-programmable gate arrays (FPGAs) can provide performance advantages with a lower resource consumption (e.g., energy) than conventional CPUs. In this paper, we show how to employ FPGAs to provide an efficient and high-performance solution for the frequent item problem. We discuss three design alternatives, each one of them exploiting different FPGA features, and we provide an exhaustive evaluation of their performance characteristics. The first design is a one-to-one mapping of the Space-Saving algorithm (shown to be the best approach in software [1]), built on special features of FPGAs: content-addressable memory and dual-ported BRAM. The two other implementations exploit the flexibility of digital circuits to implement parallel lookups and pipelining strategies, resulting in significant improvements in performance. On low-cost FPGA hardware, the fastest of our designs can process 80 million items per second--three times as much as the best known result. Moreover, and ...