Inclusion Criteria:  All patients, with a clinical diagnosis of A-T who have attended the UK's National Ataxia-Telangiectasia clinic in Nottingham or the national adult A-T service in Papworth, of any age  Exclusion Criteria:  Patients aged 16 and over who specifically inform us that they do not want their clinical data included in the study. Patients aged under 16 whose parents / guardian inform us that they do not want their child's clinical data included in the study.