It was shown that the molecular-mass distributions of hydrocarbons formed on a Co-ThO(2)-MgO-kieselguhr industrial catalyst at 1MPa pressure differ from those found at low pressures and are adequately described by the previous mathematical model based on the data obtained on cobalt catalysts at high pressures. This indicates that secondary Fischer-Tropsch synthesis reactions at moderate pressures mainly follow the mechanism characteristic of high pressures. The causes of deviations of molecular-mass distributions of hydrocarbons formed under these conditions from the Anderson-Schulz-Flory ideal distribution with an increase in the synthesis temperature are discussed.