TGF alpha and beta expression was examined using rabbit polyclonal antibodies and immunohistochemistry on a series of 195 breast carcinomas. TGF alpha immunoreactivity was observed in all but nine of the tumours, with over 50 per cent staining strongly. The polyclonal TGF alpha antibody (CIM1), when compared with a commercially available mouse monoclonal TGF alpha antibody used on the same sections, gave a good correlation (r=0.52, P<0.001). Both TGF alpha antibodies produced a granular cytoplasmic staining pattern, that with CIM 1 being coarser, suggestive of binding to an aggregated protein or organelle. Eighty‐one per cent of tumours stained with the TGF beta antibody, 35 per cent strongly. There was significant co‐expression of TGF alpha and TGF beta (P<0.001). However, they were not found to be useful prognostic indicators, lacking any significant correlation with histological classification, tumour size, nodal status, oestrogen receptor status, S‐phase fraction, or overall survival over a 9–12 year period. The expression of these growth factors in most breast carcinomas suggests that they have important biological roles, but the exact nature of these roles remains unclear at the moment.