The purpose of this study was to demonstrate the early features of the Wallerian degenerative process and their relationship with the severity of motor deficit. Fourteen patients with infarction or hemorrhage of the basal ganglia were studied by MRI of the same coronal slice along the pyramidal line. The earliest sign of abnormal signal intensity was detected 0.7 month after the initial insult. On proton-density (PD) imaging, low signal intensity was observed on 11 (73.3%) of 15 occasions from 0.7 to 2.0 months, and abnormal signal intensity was not detected 5 (83.3%) of 6 times from 2.1 to 3.7 months. High signal intensity was revealed on 11 (78.6%) of 14 occasions after 3.8 months. The widest extent of the low-intensity signal band on PD imaging was closely related to the severity of motor deficits at > 4 months. The development of the Wallerian degenerative process was divided into four stages by MRI. We conclude that the extent of Wallerian degeneration is related to the severity of motor deficit.