Cobalt supported on different gamma-alumina carries prepared by incipient wetness impregnation are used to investigate the effect of support on the performance of cobalt catalysts for Fischer-Tropsch synthesis (FTS). It is found that the acidity of support has a great influence on the interaction between metallic cobalt and support and then the reducibility of cobalt. The support with low acidity leads to the higher active FTS catalysts. Furthermore, the high reducibility and more bridged type CO which is favored by gamma-alumina with low acidity appears to be responsible for high C-5(+) hydrocarbon selectivity and low methane selectivity. (C) 2002 Elsevier Science Ltd. All rights reserved.