In a method for the intermittent occlusion of a vein draining the organ system, in which the vein is occluded by an occlusion device, the fluid pressure in the occluded vein is continuously measured and stored, the behavior of the fluid pressure is determined as a function of time, and the occlusion of the vein is triggered and/or released as a function of at least one characteristic value derived from the pressure measurements, pressure is applied during the occlusion in a pulsating manner. The device for the intermittent occlusion of a vein, including an occlusion device, a pressure measuring device for continuously measuring the fluid pressure in the occluded vein, and a memory for storing the fluid pressure behavior as a function of time, means are provided for applying a pulsating pressure in the occluded vein.