Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al2O3 catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature, synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al2O3 was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction.