Certain biochemical characteristics of pentosan polysulfate (SP 54) indicated possible antiphlogistic properties of this substance. Our extensive investigations with different models of acute inflammatory reactions (rat paw edema induced by hyaluronidase, trypsin, carrageenin or kaolin) have shown that pentosan polysulfate has a pronounced anti-inflammatory and antiphlogistic effect, although it has no analgetic properties. In contrast to other well-known antiphlogistic drugs, such as salicylate, pyrazolone or anthranilic acid derivatives, pentosan polysulfate exerts its strong anti-inflammatory effect on all types of experimental edema. This outstanding antiphlogistic and anti-inflammatory potency of pentosan polysulfate can be explained by a suppression of hyaluronidase, histamine and certain complement factors as well as by its specifically vasotropic and stabilizing effects.