Immuno-analogues of erythrocyte protein 4.2 were examined in rat thyroid tissues by immunohistochemical techniques. Immunofluorescence microscopy revealed that the peripheral cytoplasm below the apical plasma membrane of follicle epithelial cells was stained with antibodies against erythrocyte protein 4.2. The staining pattern was similar to that obtained with anti-ankyrin antibodies. The present and our recent results showing the presence of spectrin, protein 4.1 and ankyrin-like proteins in thyroid tissues indicate that most features of the erythrocyte membrane skeletal architecture are also expressed by thyroid follicle epithelial cells.