Abstract: A method and device for continuously producing slabstock polyurethane foam wherein a polymerizable reaction mixture containing a blowing agent is applied onto a moving conveyor and allowed a free rise expansion and polymerization within a substantially closed space. The pressure in this space is maintained within a predetermined pressure range by continuously supplying gas to the space, in addition to the blowing gas produced by the reaction and by simultaneously exhausting gas from said space. In this way, pressure fluctuations are reduced in the space and further parameters such as the temperature can be controlled so as to enable production of a foam with constant properties.