Background.- Ataxia-telangiectasia is a syndro¬me of autosomal recessive inheritance characteri¬zed by cerebellar ataxia, oculocutaneous telangi-ectasias variable immune system defects, chronic progressive sinopulmonary disease and a high in¬cidence of cancer. Observation.- Clinical and laboratory findings of five cases with ataxia telangiectasia were studi¬ed between years of 1992-1994. Ophthalmologic, central nervous system and immune system symp¬toms were present in all cases, however muscu-loskleton system and skin involvement were pre¬sent in only two cases. Two cases died as results of complications of recurre-nt sinopulmonary infecti¬ons.