Ataxia telangiectasia (A-T) is a devastating human recessive disorder characterized by progressive cerebellar ataxia, immunodeficiency, chromosomal instability, and cancer susceptibility. In addition to that, a high percentage of patients show dystrophy, growth retardation and poor weight gain. There are only a few studies assessing this problem and the exact variations concerning body composition, muscle strength and hormonal status are widely unknown.