OBJECTIVE: To determine the molecular defects of β-thalassemia intermedia in Guangdong Province and to provide basis for gene diagnosis and gene therapy of this disorder. METHODS: DNA analysis of the α, β and γ globin genes was performed in 18 children with β-thalassemia intermedia from Guangdong Province using polymerase chain reaction (PCR ), microarray technique, Southern blot and direct sequencing. RESULTS: Of the 18 patients,one was identified as the homozygote of TATA box-28 (A→G) change, one as the homozygote of βE26 (G→A) mutation, ten as compound heterozygotes of TATA box- 28(A→G) mutation with other β-globin mutations, two as compound heterozygotes of βE26 (G→A ) mutation with other β globin mutations, and four as double heterozygotes for β globin and α globin mutations including -SEA and -α4.2. CONCLUSIONS: The molecular defects of β- thalassemia intermedia in Guangdong Province were highly heterogeneous and its spectrum was different from the reports from other provinces of China.［Chin J Contemp Pediatr, 2007, 9 (4):358-360］