We recently described a "non-random" sequencing procedure for DNA inserts in bacteriophage M13 using Bal 3 nuclease and the dideoxy chain termination method (Poncz, M., Solowiejczyk, D., Ballantine, M., Schwartz, E., and Surrey, S. (1982) Proc. Natl. Acad. Sci. U. S. A., in press). Using this procedure, we have determined the nucleotide sequence of a cloned human beta-globin gene from a Kurdish Jew with beta +-thalassemia major. Comparison with the previously reported human beta-globin gene sequences (1-3) reveals a change in the "T-A-T-A" box. This region 5' to the capping site was previously demonstrated to be critical for the proper transcription in vitro of several different eukaryotic genes (4-7). This is the first report of a T-A-T-A box modification found in association with a spontaneously occurring human genetic disorder. In addition to this mutation, other base changes, an insertion, and a deletion in the cloned gene were found in the 5' and 3' flanking regions.