Selective catalytic reduction (SCR) of NOx has been tested using different hydrocarbons as reducing agents over an Ag/Al2O3 catalyst, both in laboratory reactors and a diesel engine test bench. The hydrocarbons tested were octane, iso-octane, octanol, octanal, octanoic acid, 1-octene, a mixture of propane-propene, dodecane, a mixture of dodecanal-dodecane and a low sulphur diesel fuel. For the C8-hydrocarbons the maximum conversions, about 80 %, occurred at a much lower temperature (down to 350 °C) and over a wider temperature range compared to the propane-propene mixture (maximum conversion at 525 °C). Also dodecane and diesel fuel gave more than 70 % conversion between 300 °C and 500 °C. In the diesel test bench a continuous NOx conversion up to 50 % was measured with a fuel penalty of 0.3-4.0 %.