An MRI-pathological correlation study was performed to determine the pathological background of white matter lesions depicted on MR images. The pathological findings were various combinations of myelin loss, axonal loss, scattered microinfarcts, astrogliosis, dilatation of perivascular space, and relative preservation of subcortical U-fibers. Concerning the dilated perivascular space, we proposed a new classification according to the present study: (1) état criblé in the basal ganglia and the thalamus, (2) état criblé in the cerebral white matter, (3) enlarged perivascular space of the lenticulostriate arteries, and (4) état criblé in other sites. In conclusion, when effects of white matter lesions on cognitive function are to be evaluated, it is necessary to clarify tissues in at least three sequences: T2-weighted, T1-weighted, and FLAIR method.