We have studied mRNA levels for a variety of growth factors in biopsy specimens from malignant, benign and normal breast tissue. We found TGFb mRNA in all breast cancers and neoplastic breast tissues but the level of the TGFb mRNA were found to be higher in breast cancer (P = 0.01). TGFa mRNA was detected in a similar proportion of cancers as in neoplastic breast tissues but the TGFa receptor EGFR mRNA was detected in only 55% of breast cancers but in all non-neoplastic breast tissue tested. The presence of EGFR mRNA was inverted related to oestrogen receptor status and coexpression of TGFa and EGFR was observed in 28% of carcinomas, and significantly more commonly in ER negative tumours (P = 0.01). PDGF a and b chain transcripts coexisted in all normal and malignant breast tissue. Insulin-like growth factor II mRNA was present in all 15 samples of non-malignant breast tissue but in only 11 of 21 (52%) of carcinomas.