OBJECTIVE: To determine the changes in basal ganglia iron content associated with various stages of idiopathic Parkinson's disease. DESIGN: Prospective magnetic resonance imaging study using a 2-T magnet. SETTING: Ambulatory care referral center. PATIENTS AND PARTICIPANTS: Forty-five patients suffering from levodopa-responsive Parkinson's disease and 45 age-matched controls. MAIN OUTCOME MEASURES: The T2 relaxation time calculated in various regions of the basal ganglia, the duration of Parkinson's disease, and the age of subjects. RESULTS: Patients with Parkinson's disease exhibited significantly decreased T2 relaxation time in the pars compacta of the substantia nigra compared with controls (P < .01), regardless of disease duration. Patients with a duration of illness above 10 years (n = 12) exhibited significantly increased T2 relaxation time in the anterior and posterior putamen (P < .005 and P < .01, respectively) and in the pallidum (P < .05) compared with age-matched controls. Putamental T2 relaxation time positively correlated with disease duration (P < .05). CONCLUSION: These results suggest that more complex brain iron changes than those previously reported are associated with idiopathic Parkinson's disease, including increased nigral iron content and decreased putamenal and pallidal iron concentration in patients with a duration of illness above 10 years.