Abstract: A method and a device for controlling the quality during the production of an extruded polymer product from a synthetic intermediate product. The production of the polymer product takes place continuously in several successive process steps; whereby a process parameter and/or a product parameter is/are detected in at least one of the process steps and is/are compared with a target value or target value range. A quality signal for determining the quality of the polymer product and/or a control signal for controlling one of the process steps is generated in accordance with this comparison. According to the invention, a measuring time and a throughput time are assigned to the process parameter and/or the product parameter, the throughput time characterizing the current material flow for the respective process step up to the production of the finished polymer product. Changes in quality can thus be identified in advance and can be taken into account for statistical process control.