Two cases of the Thai thalassemia patients with compound heterozygosities for (deltabeta)(0)/beta(0)-thalassemia and (deltabeta)(0)-thalassemia/hemoglobin E have been reported. The first case was a 8-yr-old boy who had the following hematologic data: Hb 6.5 g/dL, Hct 20.5%, MCV 70.4 fL, MCH 22.3 pg and MCHC 31.7 g/dL. Hemoglobin analysis revealed 1.9% hemoglobin A2 and 91.7% hemoglobin F. The second case, with Hb 13.9 g/dL, Hct 41.5%, MCV 69.5 fL, MCH 22.5 pg and MCHC 32.2 g/dL, was a 16-yr-old male who had 46.1% hemoglobin E and 49.8% hemoglobin F. Globin gene analyses showed that both probands carried the same deletional type (deltabeta)(0)-thalassemia trans to the 4 bp deletions in codons 41/42 beta(0)-thalassemia and to the betaE-globin gene, respectively. Polymerase chain reaction and DNA sequence analyses demonstrated that the 5' breakpoint of the (deltabeta)(0)-thalassemia deletion was located in the second intron of the delta-globin gene and that the 3' breakpoint lay within a cluster of LI repetitive sequences at 4.7 kb 3' to the beta-globin gene.