Women who have palpable breast cysts lined by apocrine metaplastic epithelium (intracystic Na/K < 3) may have a higher risk of breast cancer than those who have breast cysts lined by flattened epithelium (intracystic Na/K > 3). Transforming growth factor-alpha (TGF-alpha) exerts a proliferative effect on many cell types and may play a role in mammary carcinogenesis. Transforming growth factor-beta (TGF-beta) stimulates the proliferation of mesenchymal cells but inhibits mammary epithelial cell proliferation and may exert a protective effect against breast cancer development. The aim of this study was to measure the distribution of TGF-alpha, TGF-beta 1 and TGF beta 2 in the two sub-groups of breast cysts. TGF-alpha was undetectable in all but 2 of the 46 samples of breast cyst fluid tested. TGF-beta 1 ranged from undetectable up to 25.4 ng/ml (n = 46) while the intracystic concentrations of TGF-beta 2 were generally higher, ranging from 0.30 ng/ml to 125 ng/ml (n = 42). There was no significant difference between the distribution of TGF-beta 1 levels in the 2 cyst groups, but TGF-beta 2 levels were significantly higher (P < 0.001) in the high electrolyte ratio group (Na/K > 3). A negative correlation was found between TGF-beta 1 and TGF-beta 2 levels in the high electrolyte ratio group (rs = 0.605, p = 0.006, n = 19). TGF-alpha is unlikely to play an important role in breast cancer development in women with palpable breast cysts. The significantly higher concentrations of TGF-beta 2 in the high electrolyte ratio group may explain, in part, the lower risk of breast cancer in this group of women.