By the help of the isolated, perfused rat liver, the influence of an immune stimulant of plant origin (Esberitox N; composition: herb. thujae occid. rec., rad. baptisiae tinct., rad. echinaceae ang. et purp.) on the activity of Kupffer cells was tested. It was shown that the phagocytosis of erythrocytes was improved significantly by the single extracts and the combination of this. The extract of thuja occidentalis had the most prominent effect on the first phase of phagocytosis, whereas the extract of echinacea purpurea dominantly influenced the phagocytosis dependent metabolism.