The levels of cell membrane epidermal growth factor receptor EGFR and cytosol (c) and nuclear (n), oestrogen (E) and progesterone (P) receptors (R) were determined in 132 specimens of primary breast cancers. In the tumours of postmenopausal women an inverse significant correlation was demonstrated between the concentrations of EGFR vs. ERc, ERn, and PRc while no such correlation was noted in the tumours of premenopausal women. Premenopausal and postmenopausal EGFR positive tumours (> or = 10 fmol/mg membrane protein) could be regarded as homogenous with respect to the concentration of ER and PR whose mean values were low and without being significantly different. EGFR negative tumours were heterogeneous with respect to the ER and PR concentrations. Postmenopausal EGFR negative (< 10 fmol/mg membrane protein) tumours had evidently higher mean values of ER and PR than premenopausal EGFR negative tumours, but these differences were statistically significant for oestrogen receptors only. The levels of ER and PR of premenopausal EGFR negative tumours were approximated to the corresponding levels of EGFR positive tumours.