Objective To investigate the expression of endocytic receptor megalin and cubilin BR>in in the developing mouse kidneys, and the correlation between the expression and the development of the renal tubules. Methods Expression of megalin and cubilin in developing mouse kidneys was examined at different embryonic days (E) using immunohistochemistry. Meanwhile, the ultrastructure of developing proximal tubules related to endocytosis was observed at transimission electron microscope level. Results At E9.5, megalin and cubilin were coexpressed in apical plasma membrane of the mesonephric ducts and mesonephric tubules. From E11 to E18, in the metanephros, the expression of both receptors were seen at the free surface and apical plasma of uretic bud, but weakly in all renal tubules of S shaped body at early differentiatial stage. With the mature of proximal tubule development, they were both confined to the brush border and the apical plasma of the proximal tubules in juxtamedullary cortex.Conclusion The endocytic receptors, megalin and cubilin are expressed in apical part of nearly all renal tubule epithelia in early development, and confined to free surface of mature proximal tubules, suggesting that with the mature of proximal tubules, the two receptors are generally involved in collaborating to facilitate, the reabsorption of ultrafiltration. BR>