Joubert's syndrome is a rare developmental defect of the cerebellar vermis associated with episodic hyperpnea and apnea, abnormal eye movements, and mental retardation. The condition is usually diagnosed clinically during the neonatal period. This article reports nine patients with the syndrome (six males, three females; ages ranging from 2.5 to 9 yrs), and describes MR imaging findings in seven of these. Besides the previously described characteristic and relatively common changes of the syndrome, the MR imaging findings in these patients revealed thinned optic tracts, enlarged temporal horns in the absence of hydrocephalus, high-signal of the cerebral periventricular white matter, abnormal signal in the decussation of the superior cerebellar peduncles, and abnormal embryonic vessels associated with the dysplastic folia of the cerebellar hemispheres.