We have identified the glucose-6-phosphate dehydrogenase mutations responsible for enzyme deficiency in nine individuals with chronic nonspherocytic hemolytic anemia. We found the variants Tokyo, Iowa, Shinshu, and Guadalajara in British subjects and Kobe in an Italian. In addition we have determined the variant Corum has the mutation 820 G-->A and have found in British subjects the mis-sense mutations 224 T-->C, 488 G-->A and 833 C-->T which have not been described before. Some, but not all, of the mutations involve amino acids located near putative substrate binding sites.