The effects of activation gas and copper promoter loading on the Fischer-Tropsch synthesis performance of potassium promoted precipitated iron-based catalysts were investigated using a continuously stirred tank reactor. In this study, CO and syngas (H-2/CO = 0.7) activated catalysts were tested after varying the copper promoter loading (0, 2 and 5 %, atomic ratios relative to iron). After attaining a steady-state conversion for the CO-activated catalysts, similar or slightly higher CO conversions were exhibited with increasing copper loading, and the induction period was reduced with increasing copper loading. Partial pressure of hydrogen in the activation gas influenced the resulting activity of the catalysts. For syngas activated catalysts, CO conversion was found to increase with increasing copper loading up to 2 %, and slightly decrease with further increases in copper (5 %) loading. For similar CO conversion levels, the selectivities were similar for the CO activated catalysts, whereas for the syngas activated catalysts, the selectivity varied with copper loading. With increasing copper loading, lower hydrocarbon (methane and C-2-C-4) selectivities decreased and the corresponding higher hydrocarbon (C-5+) selectivity increased.