The clinical courses and long-term prognoses in 16 young patients with infarctions of the basal ganglia were evaluated and the recent magnetic resonance imaging findings in 9 of them were examined. Only 5 of 14 patients (35%) had motor sequelae, 4 had hemiparesis, and 1 had gait disturbance. Secondary dystonia occurred in 1 patient. Magnetic resonance imaging disclosed a circumscribed lesion in the basal ganglia, as reflected by T2 high- and T1 low-intensity signals, in all patients. The abnormal region on T2-weighted images usually was more extensive than that observed on T1-weighted ones. The hemiplegic patients each had an area of abnormal intensity in the internal capsule or corona radiata with relatively high signals on the T2- and proton-density-weighted images. Mild to moderate asymmetric atrophy of the midbrain on the side ipsilateral to the stroke lesion was observed in 8 of 9 patients. The mechanism involved may be remote transsynaptic neuronal death of the substantia nigra, as well as Wallerian degeneration of the pyramidal tract.