Transforming growth factor beta (TGF-beta) comprises a group of multifunctional regulatory proteins, whose effects include stimulation of extracellular matrix formation and modification of immune function. The presence of TGF-beta 1 and TGF-beta 2 in invasive breast carcinomas has been determined and related to pathological features, the presence of fibronectin and tenascin and lymphocyte/macrophage infiltration, using immunohistochemistry. Differences were observed in the extent of reactivity within the same carcinoma and between tumours stained with an antibody detecting TGF-beta 1 ane one detecting TGF-beta plus TGF-beta 2, the latter having a higher level of reactivity. Prominent reactivity for TGF-beta 1 was associated with lymph node metastasis, (0.02 > P > 0.01), increased detection of cellular fibronectin, fine stromal fibronectin staining, more prominent reactivity for tenascin (0.02 > P > 0.01), the presence of tumour-associated macrophage infiltration and altered ratios of CD4 and CD8 lymphocyte populations, with CD8 lymphocytes predominating. These associations were not observed for carcinomas showing prominent staining with antibody detecting TGF-beta 2 as well as TGF-beta 1. The findings indicate that TGF-beta 1 may have a role in invasion and metastasis of breast carcinomas.