Heterogenity in the clinical mainfestaions of β thalassemia may result from the presence of mild thalassemia mutations, continuous synthesis of γ globin into adult life.22 cases of β thalassemia were screened for the most common seven genetic mutations of thalassemia evaluated in Egypt studies: IVS1-6, IVS1-110, IVS2-1, IVS2-745, IVS1-1, -87 and codon 39, also screened for -158 Xmn-1 polymorphism.The frequency of IVS1-6 was found to be 22.7%, IVS1-110 was found to be 18.2%, IVS2-1, IVS2-745, IVS1-1, -87 and codon 39, were undetected.The -158 Xmn-1 polymorphism was detected in 2 out of 22 cases (9%).