Cerebellar ataxias (CA) and spastic paraplegias (SP) are genetically and clinically very heterogeneous. More than 40 loci are already known but the number of phenotypes is even greater suggesting further genetic heterogeneity. These progressive disorders are often severe and fatal, due to the absence of specific therapy. The SPATAX network combines the experience of European clinicians and scientists working on these groups of diseases. Over the past year, they have assembled the largest collection of families and achieved a number of tasks (initiation of a clinical and genetic database, distribution of DNA to participating laboratories, mapping of three new loci, and refinement of several loci). In addition to clinicians from Europe and Mediterranean countries, who play a major role in collecting families according to evaluation tools developed and validated by the SPATAX members, the group includes major European laboratories devoted to the elucidation of the molecular basis of these disorders. Each laboratory will centralize all families with a subtype of autosomal recessive (AR) CA (n=116) or SP (n=207) in order to efficiently map and identify the responsible gene(s). Genome-wide scans are already underway in 61 families. Given the expertise of the participants, the researchers expect to map and identify several genes during the course of this project. The spectrum of mutations and phenotype/genotype correlations will be analysed thanks to this unique series of patients with various phenotypes. The knowledge gained will be immediately applicable to patients in terms of improved positive diagnosis, follow-up and appropriate genetic counselling. In the long term, models for genetic entity will be developed in order to understand the pathophysiology and to identify new targets for treatment. The series of patients assembled and the precise knowledge of natural history will facilitate the implantation of therapeutic trials based on rational approaches.