erebellar ataxia is a failure in muscular coordination that re C sults from a slow, progressive deterioration of neurons in the cerebellum. An estimated 150,000 people are affected by the he reditary ataxias and related disorders in the United States. At present, there is no known cure. In an experimental treatment aimed at reconstructing the damaged pathway through exog enous neuronal supplementation, genetically ataxic mice have been used for intracerebral grafting of genetically healthy cerebellar neuroblasts, and evidence has been obtained for graft-induced en hancement of behavioral responses after bilateral cerebellar grafts. Such results are encouraging and underscore the potential of the neural grafting technique in restoring cerebellar function. How ever, many of the pathological and biochemical mechanisms in the interaction between grafted tissue and the host brain need to be further elucidated in extensive experimental studies, and great cau tion must be used in contemplating the theoretical feasibility of a possible application in humans.