One of 4 siblings affected by hereditary spinocerebellar ataxia (HSCA) of Marie's type developed Hodgkin's disease (HD): the stage was IV B, the patient was submitted to conventional chemo- and radiotherapy and achieved complete remission. An accurate clinical, genetic and immunological study was carried out on all his family, including a complete HLA typing, a chromosome study, the immunophenotyping of peripheral blood mononuclear cells (PBMC), the PBMC response to polyclonal mitogens, to interleukin 2 (IL-2), to the association of PHA + IL-2 and the evaluation of the IL-2 receptor expression. No association was clearly demonstrable between an HLA haplotype and HSCA, while the patient with HSCA and HD was HLA-B18- and DQw3-positive (the last at homozygous level), two antigens known to be strongly associated with HD, mainly among the Sardinian ethnic group. The mode of inheritance of HD susceptibility is however completely different from that of Marie's HSCA. The chromosome study did not show any characteristic pattern of the karyotype, neither of the HSCA affected nor of the unaffected members. The immunological investigations did not elucidate any characteristic behavior of the family members, apart from the typical findings of HD seen on patients with HSCA and HD. Our study could not demonstrate any genetic and/or immunologic common background shared by the two diseases, HSCA and HD. Their coexistence in our patient, although the statistic probability is very low, seems to be a fortuitous coincidence more than the result of a common genetic and pathogenetic mechanism.