According to the oxidative stress theory iron may play an important role in the pathogenesis of neurodegenerative diseases, as e.g. Parkinson's disease (PD). This review presents the results of studies, obtained by various methods, of iron in substantia nigra (SN) - a cerebral structure which degenerates in PD - and shows controversies concerning the amount of iron, its redox state, and the iron binding compounds. Taking into account all published experimental results, the increase in the concentration of iron in parkinsonian SN vs. control may be estimated as (3 + - 5)%. The presence of large amounts of divalent iron in post mortem SN can be unequivocally negated. It is, however, still possible that iron is involved in the pathogenesis of PD, as even minor changes in the amount and form of iron may initiate processes leading to cells death.