Much progress has been made in the early diagnosis of ataxia-telangiectasia since the gene was cloned in 1995, A clinical diagnosis can now be confirmed by radiosensitivity testing (colony survival assay), immunoblotting, and mutation detection. The diagnostic value of serum alpha-fetoprotein levels and radiosensitivity has been reevaluated using patients with diagnoses based on the presence of mutations in the ATM gene and the absence of ATM protein in nuclear extracts. Little progress has been made in treating the progressive ataxia.