The activity and characteristics of the nitrate derived Co/SiO2 were determined in relation to reductive pretreatment. With increasing reduction temperature (300-450 degrees C), the extent of reduction increased. This increase was not, however, accompanied with increased chemisorption capacity. Namely, the hydrogen chemisorption was highest at a reduction temperature of approx. 300 degrees C. Also, the carbon monoxide adsorption was almost constant at 200-400 degrees C, and decreased drastically thereafter. Thus, the results suggest that cobalt agglomerated at temperatures above 400 degrees C. The activity in toluene hydrogenation correlated well with the hydrogen uptake for reduction temperatures of above 300 degrees C, Also, the CO hydrogenation activity of the catalyst decreased with increasing temperature of reduction (400-450 degrees C) due to the decrease in the number of active sites.