Fischer-Tropsch synthesis can convert a variety of synthesis gas mixtures produced from both coal and natural gas to obtain hydrocarbons, which can be further processed to manufacture automotive fuels. As the Fischer-Tropsch reaction is highly exothermic, a slurry phase reactor offers a significant advantage over the traditional fixed bed reactor for heat management. Since 1992, Air Products and DOE have been developing the slurry phase Fischer-Tropsch synthesis process with help of a number of industrial partners. This paper discusses the evolution of the technology through four pilot plant campaigns conducted at DOE`s Alternative Fuels Development Unit in LaPorte, Texas. Key issues such as catalyst-wax separation, reactor productivity improvements, reactor temperature control, and in-situ activation are addressed.