The effects of the H-2/CO ratio, pressure, temperature, and the reaction-gas recycle ratio on the selectivity for hydrocarbons (HCs), including long-chain C35+ HCs, in the Fischer-Tropsch synthesis over a supported industrial cobalt-silica gel catalyst have been studied. The synthesis parameters have been as follows: a pressure of 2.0 or 6.0 MPa, an H-2/CO ratio of 1-5, a recycle ratio of 2-6, a temperature of 150-240A degrees C, and a gas hourly space velocity of 1000 h(-1). It has been shown that gas recycling provides thermal stability in the catalyst bed, significantly increases the yield of C35+ HCs, and makes it possible to control the group and fractional composition of the synthesis products.