The work at the CAER has focused on the development of a family of iron catalysts with different alpha values with the objective of providing the option of producing a broad slate of fuel and chemical products. To make a valid comparison of iron and cobalt catalysts with respect to activity and selectivity, the conversions with the iron catalysts have been carried out over wide ranges of operating conditions including pressure, temperature, H-2/CO ratios, diluent gases (both inert and reactive) and conversion levels. As an approach to define the extent of secondary reactions in determining the products that are produced, a variety of isotopically labeled olefins, alcohols and carbon dioxide have been utilized. The extent of incorporation of these compounds can be defined by determining the isotopic distribution in the products. Catalyst samples, withdrawn from the reactor during synthesis, have been characterized to define changes that occur during catalyst use. (C) 2003 Elsevier B.V. All rights reserved.