Fischer-Tropsch synthesis on a large scale is of interest as a means for conversion of remote natural gas to high-quality products, particularly liquid transportation fuels. Recent developments have resulted in reactors of advanced design having production capacities of 2500 bbl/day or higher, which is more than two orders of magnitude higher than the productivity of classical reactors operated before or during World War II. Some fundamental aspects of these reactors, which belong to the classes of gas-solid fluidized beds, multitubular trickle-beds, and slurry bubble columns are discussed to aid selection and design of reactors for a specific application. Special attention is given to scaling up of slurry bubble columns. A scaling-up strategy is proposed which might obviate the inclusion of a costly demonstration stage in the development of a novel process using bubble columns.