A process for removing catalyst fines from the wax product produced in a slurry Fischer-Tropsch reactor comprises removing the wax product from the reactor and separating the catalyst fines by passing the wax product through a high gradient magnetic field, whereby the catalyst fines are held by a magnetized filter element and the wax product passes through unhindered to form a purified wax product which is ready for upgrading. The separated catalyst fines are returned to the reactor by backwashing the filter element.