Ruthenium-promoted gamma-Al2O3-supported cobalt catalysts were prepared by different slurry impregnation methods and calcined in a hydrogen/air atmosphere. The prepared catalysts were well characterized by N-2 physisorption, TPR, XRD, TEM and XPS techniques. The addition of Ru caused the reduction peaks to shift towards lower temperatures due to the spillover of hydrogen from the Ru species. The ruthenium-promoted catalyst calcined under a hydrogen atmosphere leads to metallic cobalt with an HCP structure and shows good catalytic activity for Fischer Tropsch Synthesis under the reaction conditions studied. The catalyst calcined under an air atmosphere leads to metallic cobalt with FCC structures and showed lower catalytic activity. It was also found that the calcination atmosphere and structure of the catalyst have a profound effect on the activity and selectivity for FT synthesis. (C) 2014 Elsevier Ltd. All rights reserved.