Iron is considered to be a possible trigger of oxidative stress leading to neurodegeneration. This mechanism of neuronal death is proposed as a cause of Parkinson disease. Although most of researchers agree with this, controversies remain regarding the amounts of iron needed for this process. According to non destructive methods of assessment of the concentration of the total iron in substantia nigra, there is no difference between PD and control. However there is no need for an increase of the total iron in parkinsonian SN to trigger the oxidative stress but only of the non-ferritin bound labile iron. Our recent studies suggest an increase of this iron in PD SN. This finding corresponds well to a decrease of L-ferritin concentration in parkinsonian SN and also to a difference of the size of iron core of ferritin between PD and control SN. The significance of these finding will be discussed.