The distribution of transforming growth factor α (TGF‐α) in human normal tissues from the uterus, Fallopian tube, ovary, small and large intestine, lung, spleen, kidney, and skin was studied by immunohistochemistry. TGF‐α was found in epidermis, bronchial epithelium, intestinal mucosa, renal tubules, endo‐ as well as in exocervical and endometrial epithelium, and in the serous epithelium of the Fallopian tube. No TGF‐α was detected in the stromal components of any of the tissues nor in any of the pre‐ and post‐menopausal ovaries studied. Twenty‐nine ovarian tumours including 23 ovarian carcinomas, one malignant mixed Muellerian tumour, two ovarian metastases of gastrointestinal carcinomas, one dysgerminoma, one sarcoma, and one fibroma were studied for TGF‐α by the same immunohistochemical method. In 25 cases, specific cytoplasmic staining for TGF‐α of epithelial tumour cells could be demonstrated. The pattern and intensity of the TGF‐α immunostain varied among the TGF‐α‐positive tumours. No TGF‐α was found by immunohistochemistry in the remaining four cases nor in the stromal tumour components of any of the lesions studied. Northern blot analysis for TGF‐α mRNA was performed on 12 of the tumours. While the immunohistochemistry and blotting results correlated well in ten cases, discordant results were obtained in two lesions. Copyright © 1990 John Wiley & Sons, Ltd.