There is herein described a Fischer-Tropsch reactor. More particularly, there is described a Fischer-Tropsch reactor that incorporates forced flow through a small pore, thick layer, monolith supported catalyst and high levels of heat transfer that is able to operate with high levels of catalyst effectiveness. The catalyst bed (103) is supported on a distinct porous structure (101) through which the syn-gas flow is forced and the catalyst layer has a thickness of more than 200 microns.