The time course of distribution of 2 endotoxic lipopolysaccharides (LPS), S. abortus equi (S form) and S. minnesota R 595 (R form, Re), in liver, lungs and kidneys was studied by the immunoperoxidase method in rats. After its uptake in the liver, both LPS were first detectable in Kupffer cells and granulocytes, the R form also in hepatocytes. A redistribution of the S-form LPS from Kupffer cells to hepatocytes was observed on Day 3 after injection. The detectability of both LPS was lost between Days 5 and 9 after injection. In the lungs both LPS were detectable later than in the liver. Here the LPS were also found in alveolar and bronchiolar macrophages, which shows that they can also be eliminated through this organ. The kidneys remained essentially free of LPS, small amounts being detectable here only in the first 24 h.