Protein biomarkers suitable for the prevention of breast cancer must be extremely sensitive, easily detectable and highly correlated with the disease. They should be expressed in the reversible phase of carcinogenesis. Among the large number of candidate tumour-associated proteins, those related to the oestrogen/chorionic gonadotropin/insulin pathway seem to be of most interest because these can be causally implicated. They presumably are the first to express differently and are open to hormonal treatments. The biomarkers that give information on membrane receptor-modulated signal transduction should be considered as well. Up to now, only tamoxifen has shown some preventive activity, suggesting that the oestrogen pathway is useful indeed. Fenretinide and recombinant human chorionic gonatotropin (hCG) are also promising. But the financial requirements and the very long assessment periods largely prevent current research. This is precisely why we badly need to give priority to molecular biology research, in particular in the protein compartment There is widespread belief that advanced proteomics together with increased informatics can provide specific combinations of disease-related expression profiles that could identify high-risk groups with much more reliability and allow us to monitor preventive strategies.