The intestinal permeability of low-molecular-weight hyaluronan (LMW-HA) was investigated by using cultured monolayers of Caco-2 cells. The amount of LMW-HA that permeated the Caco-2 monolayers was measured by a carbazole assay. The permeability of LMW-HA increased inversely with the molecular size and was dose-dependent. The transport was observed to be energy-independent, and was correlated with the tight junction (TJ) permeability. These results suggest that LMW-HA permeated the Caco-2 cell monolayers via the paracellular pathway.