In recent years, the involvement of the immune system in acquired forms of cerebellar ataxia has been frequently demonstrated. In this study, we describe 6 out of 49 patients with subacute or chronic progressive cerebellar ataxia in whom antibodies against neuronal and non-neuronal antigens were identified. Two women had anti-Yo antibodies; two patients had anti-gliadin antibodies in the presence of celiac disease; one patient had a complex autoimmune disorder associated with anti-Ro-52/SS-A and anti-muscle-specific kinase antibodies, and a patient developed subacute cerebellar syndrome associated with the presence of a prostatic adenocarcinoma and atypical antibodies reacting both with cerebellar tissue and with the prostatic tumor. Our study confirms previous findings in paraneoplastic syndromes, and indicates that at least 10% of sporadic cerebellar ataxia may be related to immune-mediated mechanisms.