A process for the conversion of synthesis gas to hydrocarbons by contacting the synthesis gas at an elevated temperature and pressure with a suspension comprising a solid particulate catalyst suspended in a liquid medium, which contacting takes place in a system comprising at least one high shear mixing zone and a reactor vessel wherein the volume of suspension present in the high shear mixing zone(s) is substantially less than the volume of suspension present in the reactor vessel, suspension is mixed with synthesis gas in the high shear mixing zone(s), the resulting mixture of suspension and synthesis gas is discharged from the high shear mixing zone(s) into the reactor vessel and wherein kinetic energy is dissipated to the suspension present in the high shear mixing zone(s) at a rate of at least 0.5 kW/m3 relative to the total volume of suspension present in the system.