We report on a Spanish family with cooccurrence of manic-depression and a form of hereditary cerebellar ataxia. All affected individuals in the second generation showed cerebellar ataxia and manic-depression simultaneously. Since anticipation has been described in both disorders and the pattern of segregation may be autosomal as well as X-linked, we have searched for a possible involvement of two candidate genes which are located either on an autosome (SCA1) or on the X-chromosome (GABRA3). We concluded that expansion of trinucleotide repeats at SCA1 gene cannot be considered as a disease-causing mutation, and this gene should be initially discarded.