We describe an African-American child with beta-thalassemia intermedia. Molecular studies revealed that the proband is a compound heterozygote for the -29 (A-->G) beta (+)-thalassemia mutation and an extensive deletion involving the delta- and beta-globin genes. The proband's mother is a simple carrier of the deletion and exhibits the phenotype of delta beta-thalassemia rather than hereditary persistence of fetal hemoglobin. The deletion spans 11,767 bp, with the 5' deletion endpoint located 2,455 bp upstream of the delta-globin gene mRNA Cap site and the 3' endpoint located 441 bp downstream of the termination codon of the beta-globin gene. Based on this information, we have developed a polymerase chain reaction strategy for the rapid detection of this delta beta-thalassemia deletion.