The concentration of neuromelanin (NM) in substantia nigra pars compacta (SNPC) has been measured in male and female normal subjects at different ages in the range 1-97 years old and in SNPC of parkinsonian patients. A very similar age trend of NM concentration was found in both sexes. In the first year of life NM was not detectable, between 10 and 20 years the NM levels were 0.3-0.8 microg/mg of SNPC, between 20 and 50 years were 0.8-2.3 microg/mg SNPC and between 50 and 90 were 2.3-3.7 microg/mg of SNPC. In parkinsonian subjects, the NM levels were 1.2-1.5 microg/mg of SNPC, which is less than 50% with respect to the age-matched controls. These data demonstrate a continuous NM accumulation in SNPC neurons during aging, the presence of large amounts of NM in SNPC and severe depletion of NM in Parkinson's disease.