Necropsy findings are reported for a case of Joubert syndrome (familiar aplasia of cerebellar vermis with episodic hyperpnea, abnormal eye-movements, ataxia and retardation). The findings consisted of an almost total aplasia of the cerebellar vermis; dysplasias and numerous heterotopias of cerebellar nuclei; an almost total absence of pyramidal decussation; and anomalies in the structure of the inferior olivary nuclei, the descending trigeminal tract, solitary fascicle and of the dorsal column nuclei. The lesion resembled the Dandy-Walker malformation or simple aplasia of the cerebellar vermis in some of its aspects, but there were numerous others to set it apart--at least tentatively--as a distinct nosologic entity.