Method to start a steady state process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas, which process comprises the steps of: (i) providing the synthesis gas; and (ii) catalytically converting the synthesis gas at an elevated temperature and a steady state total reactor pressure to obtain the normally gaseous, normally liquid and optionally normally solid hydrocarbons; the method comprising admixing the synthesis gas of step (i) with one or more inert gases to form an admixture stream prior to catalytically converting the synthesis gas in step (ii) at the steady state total reactor pressure and wherein as the activity of the catalyst converting the synthesis gas proceeds towards a steady state, the amount of inert gas(es) in the admixture stream is reduced.