Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked hemolytic enzymopathy affecting 3% of Southern Chinese males. Among 275 adult allogeneic hematopoietic stem cell transplantations (SCT), five cases (1.8%) each of donors and recipients were G6PD deficient. Among 107 autologous SCT, four patients (3.7%) were G6PD deficient. All subjects were male, except for two female patients with chronic myeloid leukemia (CML). The incidence of G6PD deficiency in female CML patients was significantly higher than the background female incidence (P = 0.004), but comparable with that in the males (P = 0.664). There was no significant hemolysis or delay in red cell engraftment, and all but one patient converted to donor G6PD screening status. One female patient achieved partial correction of her G6PD status and relapsed at 10 months. We suggest that G6PD deficiency should be tested for in all marrow donors and recipients in susceptible populations. From our data, there is a suggestion of increased clinical incidence of G6PD deficiency in female patients with multi-lineage clonal marrow disorders.