The clinical classification of autosomal dominant cerebellar ataxias (ADCAs) is intricate due to the variable and unpredictable association of signs and symptoms of central nervous system (CNS) and peripheral nervous system (PNS) deterioration during the life of a patient. However, for many purposes, particularly patient management, clinical systematics is the most useful method for labelling patients; in some instances there is no basis for any more fundamental classification of phenotypes. On the other hand, recent molecular-genetic approaches to dominant ataxias have had a profound impact in nosology, diagnostic procedures and the management of patients, since they are based on the fact that all mendelian neurological diseases can be precisely classified according to the locus involved as well as the particular mutant allele at that locus. Therefore, a clinical and genetic classification of dominant ataxias is herewith proposed as the best nosographical choice. Clinical, neuropathological, genetic, and pathogenetic aspects of ADCAs are reviewed and discussed to help the clinical neurologist guide diagnostic procedures and manage ataxic patients.