Cerebellar abiotrophy in Arabian horses clinically manifests itself early in the life of affected individuals as ataxia, an intention head tremor, and lack of a menace blink response. Histopathologically, there is a marked loss of Purkinje neurons. The etiology of this disease has remained undetermined; viral isolation studies in affected individuals have been unrewarding. A hereditary basis for this disease has been proposed. This report reviews the pertinent neuroanatomy, clinical signs, histopathology, and includes the preliminary results of a pedigree analysis of fifty affected individuals.