Intrinsic rates for the Fischer‐Tropsch synthesis reaction over a promoted iron catalyst fabricated at the Research Institute of the Petroleum Industry (RIPI) have been obtained in the temperature range of 290°C to 310°C, pressure range of 1500 to 2300 kPa, molar hydrogen to carbon monoxide ratio of 0.76 to 1.82, and a space velocity of 3300 h−1 under conditions of constant catalyst activity. To this end, the initial reaction rates have been measured at constant temperature (±1°C) in the absence of diffusion limitations, and power‐law equations have been fitted in terms of the hydrogen and carbon monoxide partial pressures for the reaction rates.