This study tested the hypothesis that diffusion tensor imaging (DTI) can detect alteration in microscopic integrity of white matter (WM) and basal ganglia (BG) regions known to be involved in Parkinson's disease (PD) pathology. It was also hypothesized that there is an association between the DTI abnormality and PD severity and subtype. DTI at 4 Tesla was obtained in 12 PD and 20 control subjects. The DTI measures of fractional anisotropy (FA) and mean diffusivity (MD) were evaluated using both region of interest (ROI) and voxel-based methods. Movement deficits in PD subjects were assessed using Motor Subscale (Part III) of the Unified Parkinson's Disease Rating Scale (UPDRS). Subtype determination of movement deficits was derived based upon results of subjects’ UPDRS ratings. Reduced FA (p<0.05, corrected) was found in PD subjects in a number of regions, including the precentral gyrus, substantia nigra, putamen, posterior striatum, frontal WM, and in regions related to the supplementary motor areas. Reduced FA in the substantia nigra correlated (p<0.05, corrected) with increased UPDRS motor scores. Significant spatial correlations between FA alterations in putamen and other PD-affected regions were also found in the context of PD subtypes index analysis. Our data suggest that microstructural alterations detected with DTI might serve as a potential biomarker for PD.