A carbon-supported cobalt nano-catalyst (Co/C) synthesized through plasma was tested for Fischer-Tropsch activity. Catalyst deactivation and activation protocols studied included in situ sample pre-treatment at 673K in gas flowing at the rate of 250cm(3)min(-1) in: (a) H-2 only, (b) CO only, and (c) CO followed by H-2, with each cycle lasting 24h. The so-treated catalyst samples were then tested for FTS activity for over 50h of time-on-stream (TOS), at 2.2MPa pressure and 493 or 518K temperature in a 3-phase continuously-stirred tank slurry reactor (3-phi-CSTSR) using squalane (C30H62) as the carrier liquid phase. The feed gas composition of molar H-2:CO=1.7 comprising 50% H-2, 30% CO, and 10% CO2 balanced in Ar for mass balance determination, flowing at a gas hourly space velocity (GHSV) of 3360cm(3)h(-1)g(-1) of catalyst. Fresh catalysts and those reduced by CO-only were completely inactive at 493K and initial inactivity was attributed to the excessive C matrix formed around the metal nanoparticles during catalyst synthesis. The sample that was reduced by H-2 only was the most active, although it showed the fastest declining activity due to cumulative high H2O vapour pressure in the FTS reactor, while the sample pre-treated in both CO and H-2 demonstrated a higher degree of stability with TOS.