Ataxia-telangiectasia is an autosomal recessive disorders characterized by cerebellar ataxis, oculocutaneous telangiectasia and frequent respiratory infections due to immunoincompetence. Ataxia usually appear by age of 2 years with most patients need wheelchairs for morbility by early teenage. Speech and eye movements are also affected. Other important features are immunodeficiency, a high level of serum alpha-fetoprotein concentration, growth retardation, telangiectasia and a very high risk of a lymphoid tumor. Patients also show an increased sensitivity to ionizing radiation. We report a case of a 7-year-old girl who had ataxic gate, conjunctival telangiectasia, and frequent upper respiratory infection. Her alpha-fetoprotein was elevated and the serum IgA was decreased. The brain MRI showed prominent cerebellar atrophy. From the 1 st year of life to death, the level of serum gamma- GTP became steadily elevated up to 10 times of a normal level.