We investigated whether in addition to the well known genetic alteration in red blood cell membrane band 3 protein, a deletion of 9 amino acids leading to ovalocytosis, other mutations to band 3 also exist. In 12% of our thalassemia major patients investigated, we found two bands in the agarose gel-electrophoresis of PCR products from band 3 gene with a difference of 65 +/- 10 bp, equivalent to a deletion of 20 to 25 amino acids in band 3 protein. Thus, a co-existing band 3-mutant allele in addition to the thalassemic globin gene defects, could also contribute to erythrocyte membrane defects and to the spectrum of clinical symptoms of these thalassemia major patients.