A series of breast cancer biopsies from 204 women were analysed immunohistochemically for the expression of transforming growth factor alpha (TGF-alpha). Expression of TGF-alpha was intense in 119 cases (58%), weak in 63 (31%), and totally absent in 22 (11%) of the cases. No correlation was observed between the expression of TGF-alpha and tumour size, metastasis at diagnosis, histological type and grade, ER and PR status, DNA index, S-phase fraction or the expression of TGF-beta1 or beta2. However, the expression of TGF-alpha was significantly related to axillary lymph node metastasis and to low survival probability during the follow-up. These data support the earlier observations on the in vitro studies, suggesting that TGF-alpha most probably exerts an in vivo growth stimulation of female breast cancer cells.