Proton magnetic resonance spectroscopy (1H-MRS), localized to the lentiform nucleus, was carried out in 12 patients with idiopathic Parkinson's disease (IPD), seven patients with multiple-system atrophy (MSA), seven patients with progressive supranuclear palsy (PSP), and 10 healthy age-matched controls. The study assessed the level of N-acetylaspartate (NAA), creatine-phosphocreatine (Cr), and choline (Cho) in the putamen and globus pallidus of these patients. NAA/Cho and NAA/Cr ratios were significantly reduced in MSA and PSP patients. No significant difference was found between IPD patients and controls. These results suggest an NAA deficit, due to neuronal loss, in the lentiform nucleus of MSA and PSP patients. 1H-MRS is a noninvasive technique that can provide useful information regarding striatal neuronal loss in basal ganglia of patients with atypical parkinsonian disorders and represents a potential tool for diagnosing these disorders.