The expression of epidermal growth factor (EGF) andc‐myconcogene product was studied immunohistochemically in 65 benign and malignant human thyroids. Normal thyroid tissues were usually negative with each antibody. Benign and malignant neoplastic thyroid tissues demonstrated a high percentage of stained cells. However, there was no significant difference in positivity between benign and malignant neoplastic tissues. In Graves' disease 25% of the cases were positive for EGF, and 100% forc‐mycproduct. The effect of EGF orc‐mycexpression on prognosis was also examined in 42 patients with papillary thyroid carcinoma. When the cases were divided into two groups with regard to their EGF staining score (highly‐expressed and poorly‐expressed groups), the frequency of highly‐expressed tumours was significantly higher in the recurrence‐positive group compared with the recurrence‐free group (86%vs57%), but there was no significant difference between the groups in respect of