The end result of our research would be the development of a new diagnostic technique that could be used as a screening test, starting from a simple blood collection, a common procedure without any risk to the subject. Red blood cells (RBC) of patients affected by breast cancer are more sensitive to the denaturing action of acetylphenylhydrazine (APH), hence the formation time of hemin, one of the last oxidation products, is significantly shorter then in normal subjects. Our previous experiment showed the differences during iron oxidation between breast cancer patients and healthy persons (Croci et al. 2001). Different amounts of hemin, after the same incubation time, can discriminate between samples collected from people suffering from cancer and a healthy population. These results have given birth to the necessity to standardise a procedure useful as a screening method. The aim of the present work was to define a range of values that characterise the samples collected from healthy people.