The modern methods of preparation of nanoparticles of metals (cobalt and iron) and their oxides are described. The results of Fischer-Tropsch synthesis in a three-phase (gas-liquid-solid) system over iron and cobalt nanocatalysts are discussed. It is noted that in most cases, nanocatalysts exhibit a higher activity in comparison with conventional catalysts that are used for the liquid-phase synthesis. Under certain conditions, the efficiency of a nanocatalyst can achieve 5 kg/(kg cat h), which is an order of magnitude higher than that of conventional catalyst systems.