The Fischer-Tropsch synthesis is at the heart of the Biomass-to-Liquids (BTL) process. Feasibility studies published in open literature typically consider cobalt-based catalysts for the Fischer-Tropsch synthesis. Here, we present an overview on the history and development up until the present for both cobalt- and iron-based Fischer-Tropsch catalysts. The role of the support material and various other additives to the catalyst formulation are discussed in detail with regard to activity, catalyst deactivation, and selectivity. Tentative explanations for e.g. the observed size dependency in cobalt-based catalysts and phase transformations in iron-based Fischer-Tropsch catalysts are offered. The productivity of cobalt-based catalysts at high conversion level is currently higher than that of iron-based catalysts. Nevertheless, it is argued that iron-based catalysts may be an attractive option for the BTL-process, since it is much cheaper, impacting on the cost of the process due to inevitable process set-ups in industrial operation. Improvement of current iron-based catalysts is however desired.