Fetal tissue repair is rapid, relatively scarless, and proceeds in an environment rich in hyaluronic acid. Understanding the interaction of hyaluronic acid (HA) with the reparative cells may provide important insight into the remarkable process of fetal wound healing. Therefore, the purpose of this study was to characterize the HA receptor (a member of the CD44 family of cell surface glycoproteins) and its density on the cell surface of fetal fibroblasts. HA receptor expression on both adult and fetal fibroblasts was first studied by Western blot analysis. Autoradiographs of the blots were assessed by densitometry to quantitate the relative amounts of the HA receptor. It appears that the HA receptor expressed on both adult and fetal rabbit dermal fibroblasts is a 56-kd protein. After normalizing for total protein concentration using the Bradford protein assay, the fetal HA receptor density was found to be approximately four-fold greater than that of the adult. The same adult and fetal fibroblasts were then studied by flow cytometry, using a fluorescence-activated cell sorter (FACS). Relative fluorescence was representative of HA receptor density. Corroborating the authors' earlier result with the Western blot analysis, the FACS analysis showed that the fetal fibroblasts had 2.5 times the fluorescence of the adult cells. It is concluded that, in comparison to adult fibroblasts, fetal fibroblasts have an increased density of cell-surface HA receptor.