This book reviews promoter effects on iron-based catalysts for Fischer-Tropsch synthesis, particularly in the use of promoters contributing to increase light olefin production and to lower methane formation operated at high reaction temperatures (T?270 centigrade). The aim of the present review is to determine how the promoters interact with iron oxide to decrease methane selectivity and to increase C2-C4 olefins selectivity. It is important to establish which promoters are potential for light olefin production and the operating conditions at which these promotion effects are mainly observed. In addition, the role of supports on iron catalyst systems is also covered in this book. Qualitatively, there is an agreement that the basicity of promoters is of importance as it leads to a strengthened iron- carbon interaction and depressed hydrogenation ability. Of all promoters considered, the study found that iron based catalysts promoted with combined potassium and manganese provided the most promising direction to light olefin production with low methane formation at high temperature.