Abstract: The sampling apparatus for a biological reactor comprises a probe housing which is connectable to a connection port of a bioreactor. A probe located within the probe housing contains a head region having a semipermeable membrane which permits the passage or throughflow of culture filtrate, but does not allow the entrance of cells. In order to avoid clogging of the semipermeable membrane, this probe is connected with a vibrator which imparts or transmits to the semipermeable membrane a preferably continual vibrating motion which preferably acts in the axial direction of the probe.