[en] Hair samples from breast cancer patients were collected at the same time as tumour and normal tissues obtained during mastectomy, in order to determine elemental concentrations and investigate whether hair can act as an epidemiological monitor of the disease. Instrumental neutron activation analysis was used and concentrations for Na, Mg, S, Cl, Ca, Mn, Cu, Zn, Br, I, Sb, Ba, Au and Hg in the hair samples measured. No strong correlations were found between the concentrations of Cl, Cu, Zn and Br in hair and those in tumour tissues and in normal tissues. The level of Zn in the patients hair is low and that of Ca very high