An autopsy case report of a Louis-Bar syndrome (Ataxia telangiectasia) is given on a 9 year-old boy who was ill for 7 years. The Louis-Bar syndrome mostly is a hereditary familial disease transmitted by an autosomal recessive gene. We are considering the syndrome as a special form of hereditary ataxias which is morphologically belonging to the systematic atrophies of the cerebellum and, above all, combined with oculo-cutaneous telangiectasia and an immunopathy. As a peculiarity the present case exhibited the existence of generalized angiectasia (cerebellum, meninges, dura mater, epiphysis, skin, eyes, lungs, spleen, kidney).