Growth factors may play an important role in tumour growth and angiogenesis by their influence on tumour cell proliferation or their effect on neovascularization. The aim of the present study was to determine which of the growth factors, growth-inhibiting factors, and their receptors investigated in a previous study are correlated with proliferation and angiogenesis in invasive breast cancer, with emphasis on the impact of possible autocrine and paracrine loops. Five growth factors and their receptors: platelet-derived growth factor A chain (PDGF-AA) and PDGF alpha receptor (PDGF alpha R), PDGF-BB and PDGF beta receptor (PDGF beta R), transforming growth factor alpha (TGF alpha) and its receptor epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGF) and its receptors (Flt-1 and Flk-1/KDR; two growth-inhibiting factors: transforming growth factor beta-1 (TGF beta 1) and TGF beta 2 and their receptor couple TGF beta R-I and TGF beta R-II; and basic fibroblast growth factor (bFGF) were stained in 45 cases of invasive breast cancer by standard immunohistochemistry on frozen sections. Staining in tumour cells, stromal cells, and endothelial cells was scored as negative or positive. Proliferation was determined by assessment of the mitotic activity index (MAI) and the degree of angiogenesis was measure by counting the number of microvessels (microvessel density: MVD) in the most vascularized area of the tumour. bFGF and EGFR showed positive correlations with the MAI, while TGF beta 2 showed a negative correlation. Expression of bFGF, TGF alpha, TGF beta 2, and EGFR correlated positively with the MVD. Co-expression of the TGF alpha/EGFR growth factor/receptor combination showed a stronger correlation with the MAI and the MVD than EGFR or TGF alpha alone, and the TGF beta 2/TGF beta R-I/TGE beta R-II combination showed a positive correlation with the MVD. In conclusion, the expression of several growth factors, growth factor receptors and growth-inhibiting factors showed correlations with the rate of proliferation and the degree of angiogenesis in invasive breast cancer. Some growth factor/receptor combinations showed stronger correlations with proliferation and angiogenesis than the growth factor or receptor alone, pointing to the importance of possible auto- and paracrine loops for stimulation of proliferation and angiogenesis by growth factors and their receptors.