Glucose-6-Phosphate Dehydrogenase (G6PD) is the most common enzymopathy of humans, affecting >400 million people. It is associated with a range of clinical manifestations such as neonatal jaundice, drug or infection-mediated hemolytic crisis, favism, and less commonly, chronic nonspherocytic anemia (CNSHA). Nearly 400 G6PD variants have been identified on the basis of their biochemical characteristics, but <60 mutations have been identified at the DNA level (Beutler, 1994). The distribution of mutations along the length of the cDNA is not random, and point mutations that cause CNSHA are largely confined to two areas: the NADP-binding domain of the enzyme and the G6P-binding region (Beutler, 1991;Vulliamy et al., 1993). However, based on the three-dimensional structure of the G6PD of the Leuconostoc mesenteroides, Mason et al. (1994) reported that these mutations might affect the residues involved in subunit contact, suggesting that they destabilize the G6PD dimer. These defects are not propagated in the population, but rather arise sporadically as new mutations. As a result, this type of G6PD deficiency is quite heterogeneous (Beutler, 1991). In this report we describe a new mutation in the exon 11 associated with CNSHA.