Fifty-nine thyroid tumors were re-examined and studied using immunohistochemistry to detect the presence of ceruloplasmin (CP), lactoferrin (LF), thyroglobulin, thyrocalcitonin, carcinoembryonic antigen and ferritin. In an attempt to study the contribution of the immunodetection of CP and LF in the diagnosis of malignant versus benign tumors, specially in follicular tumors, we compared our results of immunodetection with those of Tuccari and Barresi, and carried out our own studies on the usefulness of these immunolabelling. Concerning CP and LF staining, we have found the following data: 1) little (in contrast to Tuccari and Barresi) or no staining in normal thyroid and benign adenomas; 2) diffuse and intense staining in papillary and follicular carcinomas (as noted by the previous authors); 3) diffuse and weak staining for medullary carcinomas (in contrast to Tuccari and Barresi who found none). Our findings suggest that a diffuse and intense cytoplasmic staining with CP and LF concerning more than one third of all cells is a criterion of malignancy, whereas a weak paranuclear staining of a few cells is more in favor of a benign process.