TiO2 was treated with boron (0.05, 0.1%: boric acid source) to give B/TiO2.CO(NO3)(2).6H(2)O(10% Co) was then added to both TiO2 and B/TiO2 (incipient wetness) and the materials were then sulfided with 100, 200 and 500 ppm (NH4)(2)S. The sulfided Co/TiO2 catalysts with and without boron were characterised by TPR and O-2 titration and evaluated for Fischer-Tropsch synthesis. Low-level sulfur addition (100, 200 ppm S) did not significantly influence the activity and selectivity of the catalysts. The addition of a higher-level loading of sulfur (500 ppm S) resulted in severe sulfur poisoning of catalysts (80% decrease in reaction rate), but the modification of Co/TiO2 by boron retarded this poisoning (35% decrease in reaction rate). A shift in the product distribution to light molecular weight hydrocarbons (alpha = 0.32) was observed for the 500 ppm S loaded catalyst (no boron addition) while boron addition retarded this shift (alpha = 0.47). The effect of boron on the sulfur poisoning resistance of the Co/TiO2 catalysts is discussed.