It has been presented the results of investigations into friction stir processing carried out on the AlSi9Mg aluminium casting alloy. The investigations referred to the determination of the influence of process conditions on the moment of force affecting the tool and on the temperature in the stirring zone. The results of the investigations have shown that the increase in the rotational speed of the tool causes the decrease in the moment affecting it and the increase in the temperature in the tool area. It has been shown also that the increase in the rate of the tool travel brings about the increase in the moment of force and small changes in the temperature. The experimental measurement results have been compared to numerical calculation ones.